From 453fa9fa1465c1da705f712261ff9e899ff29fff Mon Sep 17 00:00:00 2001 From: matianjun1 Date: Sun, 18 Jun 2017 22:46:28 +0800 Subject: [PATCH] add exercise with hint --- ...ynb => 100 Numpy exercises with hint.ipynb | 284 ++++++++----- ...ion.md => 100 Numpy exercises with hint.md | 378 +++++++++++++----- 2 files changed, 472 insertions(+), 190 deletions(-) rename 100 Numpy exercises with suggestion.ipynb => 100 Numpy exercises with hint.ipynb (81%) rename 100 Numpy exercises with suggestion.md => 100 Numpy exercises with hint.md (56%) diff --git a/100 Numpy exercises with suggestion.ipynb b/100 Numpy exercises with hint.ipynb similarity index 81% rename from 100 Numpy exercises with suggestion.ipynb rename to 100 Numpy exercises with hint.ipynb index 7905b84..d9dd849 100644 --- a/100 Numpy exercises with suggestion.ipynb +++ b/100 Numpy exercises with hint.ipynb @@ -4,7 +4,7 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "# 100 numpy exercises with suggestion\n", + "# 100 numpy exercises with hint\n", "\n", "This is a collection of exercises that have been collected in the numpy mailing list, on stack overflow and in the numpy documentation. The goal of this collection is to offer a quick reference for both old and new users but also to provide a set of exercices for those who teach.\n", "\n", @@ -16,7 +16,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 1. Import the numpy package under the name `np` (★☆☆) (suggestion: import … as ..)" + "#### 1. Import the numpy package under the name `np` (★☆☆) \n", + "##### (hint: import … as ..)" ] }, { @@ -32,7 +33,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 2. Print the numpy version and the configuration (★☆☆) (suggestion: np.\\_\\_verison\\_\\_, np.show\\_config)" + "#### 2. Print the numpy version and the configuration (★☆☆) \n", + "##### (hint: np.\\_\\_verison\\_\\_, np.show\\_config)" ] }, { @@ -48,7 +50,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 3. Create a null vector of size 10 (★☆☆) (suggestion: np.zeros)" + "#### 3. Create a null vector of size 10 (★☆☆) \n", + "##### (hint: np.zeros)" ] }, { @@ -64,7 +67,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 4. How to find the memory size of any array (★☆☆) (suggestion: size, itemsize)" + "#### 4. How to find the memory size of any array (★☆☆) \n", + "##### (hint: size, itemsize)" ] }, { @@ -80,7 +84,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 5. How to get the documentation of the numpy add function from the command line? (★☆☆) (suggestion: np.info)" + "#### 5. How to get the documentation of the numpy add function from the command line? (★☆☆) \n", + "##### (hint: np.info)" ] }, { @@ -96,7 +101,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 6. Create a null vector of size 10 but the fifth value which is 1 (★☆☆) (suggestion: array\\[4\\])" + "#### 6. Create a null vector of size 10 but the fifth value which is 1 (★☆☆) \n", + "##### (hint: array\\[4\\])" ] }, { @@ -112,7 +118,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 7. Create a vector with values ranging from 10 to 49 (★☆☆) (suggestion: np.arange)" + "#### 7. Create a vector with values ranging from 10 to 49 (★☆☆) \n", + "##### (hint: np.arange)" ] }, { @@ -128,7 +135,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 8. Reverse a vector (first element becomes last) (★☆☆) (suggestion: array\\[::-1\\])" + "#### 8. Reverse a vector (first element becomes last) (★☆☆) \n", + "##### (hint: array\\[::-1\\])" ] }, { @@ -144,7 +152,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 9. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆) (suggestion: reshape)" + "#### 9. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆) \n", + "##### (hint: reshape)" ] }, { @@ -160,7 +169,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 10. Find indices of non-zero elements from \\[1,2,0,0,4,0\\] (★☆☆) (suggestion: np.nonzero)" + "#### 10. Find indices of non-zero elements from \\[1,2,0,0,4,0\\] (★☆☆) \n", + "##### (hint: np.nonzero)" ] }, { @@ -176,7 +186,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 11. Create a 3x3 identity matrix (★☆☆) (suggestion: np.eye)" + "#### 11. Create a 3x3 identity matrix (★☆☆) \n", + "##### (hint: np.eye)" ] }, { @@ -192,7 +203,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 12. Create a 3x3x3 array with random values (★☆☆) (suggestion: np.random.random)" + "#### 12. Create a 3x3x3 array with random values (★☆☆) \n", + "##### (hint: np.random.random)" ] }, { @@ -208,7 +220,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 13. Create a 10x10 array with random values and find the minimum and maximum values (★☆☆) (suggestion: min, max)" + "#### 13. Create a 10x10 array with random values and find the minimum and maximum values (★☆☆) \n", + "##### (hint: min, max)" ] }, { @@ -224,7 +237,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 14. Create a random vector of size 30 and find the mean value (★☆☆) (suggestion: mean)" + "#### 14. Create a random vector of size 30 and find the mean value (★☆☆) \n", + "##### (hint: mean)" ] }, { @@ -240,7 +254,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 15. Create a 2d array with 1 on the border and 0 inside (★☆☆) (suggestion: array\\[1:-1, 1:-1\\])" + "#### 15. Create a 2d array with 1 on the border and 0 inside (★☆☆) \n", + "##### (hint: array\\[1:-1, 1:-1\\])" ] }, { @@ -256,7 +271,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 16. How to add a border (filled with 0's) around an existing array? (★☆☆) (suggestion: np.pad)" + "#### 16. How to add a border (filled with 0's) around an existing array? (★☆☆) \n", + "##### (hint: np.pad)" ] }, { @@ -272,7 +288,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 17. What is the result of the following expression? (★☆☆) (suggestion: NaN = not a number, inf = infinity)" + "#### 17. What is the result of the following expression? (★☆☆) \n", + "##### (hint: NaN = not a number, inf = infinity)" ] }, { @@ -301,7 +318,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 18. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆) (suggestion: np.diag)" + "#### 18. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆) \n", + "##### (hint: np.diag)" ] }, { @@ -317,7 +335,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 19. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆) (suggestion: array\\[::2\\])" + "#### 19. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆) \n", + "##### (hint: array\\[::2\\])" ] }, { @@ -333,7 +352,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 20. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element? (suggestion: np.unravel_index)" + "#### 20. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element? \n", + "##### (hint: np.unravel_index)" ] }, { @@ -349,7 +369,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 21. Create a checkerboard 8x8 matrix using the tile function (★☆☆) (suggestion: np.tile)" + "#### 21. Create a checkerboard 8x8 matrix using the tile function (★☆☆) \n", + "##### (hint: np.tile)" ] }, { @@ -365,7 +386,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 22. Normalize a 5x5 random matrix (★☆☆) (suggestion: (x - min) / (max - min))" + "#### 22. Normalize a 5x5 random matrix (★☆☆) \n", + "##### (hint: (x - min) / (max - min))" ] }, { @@ -381,7 +403,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 23. Create a custom dtype that describes a color as four unsigned bytes (RGBA) (★☆☆) (suggestion: np.dtype)" + "#### 23. Create a custom dtype that describes a color as four unsigned bytes (RGBA) (★☆☆) \n", + "##### (hint: np.dtype)" ] }, { @@ -397,7 +420,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 24. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆) (suggestion: np.dot | @)" + "#### 24. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆) \n", + "##### (hint: np.dot | @)" ] }, { @@ -413,7 +437,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 25. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆) (suggestion: >, <=)" + "#### 25. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆) \n", + "##### (hint: >, <=)" ] }, { @@ -429,7 +454,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 26. What is the output of the following script? (★☆☆) (suggestion: np.sum)" + "#### 26. What is the output of the following script? (★☆☆) \n", + "##### (hint: np.sum)" ] }, { @@ -515,7 +541,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 29. How to round away from zero a float array ? (★☆☆) (suggestion: np.uniform, np.copysign, np.ceil, np.abs)" + "#### 29. How to round away from zero a float array ? (★☆☆) \n", + "##### (hint: np.uniform, np.copysign, np.ceil, np.abs)" ] }, { @@ -531,7 +558,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 30. How to find common values between two arrays? (★☆☆) (suggestion: np.intersect1d)" + "#### 30. How to find common values between two arrays? (★☆☆) \n", + "##### (hint: np.intersect1d)" ] }, { @@ -547,7 +575,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 31. How to ignore all numpy warnings (not recommended)? (★☆☆) (suggestion: np.seterr, np.errstate)" + "#### 31. How to ignore all numpy warnings (not recommended)? (★☆☆) \n", + "##### (hint: np.seterr, np.errstate)" ] }, { @@ -563,7 +592,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 32. Is the following expressions true? (★☆☆) (suggestion: imaginary number)" + "#### 32. Is the following expressions true? (★☆☆) \n", + "##### (hint: imaginary number)" ] }, { @@ -588,7 +618,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 33. How to get the dates of yesterday, today and tomorrow? (★☆☆) (suggestion: np.datetime64, np.timedelta64)" + "#### 33. How to get the dates of yesterday, today and tomorrow? (★☆☆) \n", + "##### (hint: np.datetime64, np.timedelta64)" ] }, { @@ -604,7 +635,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 34. How to get all the dates corresponding to the month of July 2016? (★★☆) (suggestion: np.arange(dtype=datetime64\\['D'\\]))" + "#### 34. How to get all the dates corresponding to the month of July 2016? (★★☆) \n", + "##### (hint: np.arange(dtype=datetime64\\['D'\\]))" ] }, { @@ -620,7 +652,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 35. How to compute ((A+B)\\*(-A/2)) in place (without copy)? (★★☆) (suggestion: np.add(out=), np.negative(out=), np.multiply(out=), np.divide(out=))" + "#### 35. How to compute ((A+B)\\*(-A/2)) in place (without copy)? (★★☆) \n", + "##### (hint: np.add(out=), np.negative(out=), np.multiply(out=), np.divide(out=))" ] }, { @@ -636,7 +669,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 36. Extract the integer part of a random array using 5 different methods (★★☆) (suggestion: %, np.floor, np.ceil, astype, np.trunc)" + "#### 36. Extract the integer part of a random array using 5 different methods (★★☆) \n", + "##### (hint: %, np.floor, np.ceil, astype, np.trunc)" ] }, { @@ -652,7 +686,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 37. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆) (suggestion: np.arange)" + "#### 37. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆) \n", + "##### (hint: np.arange)" ] }, { @@ -668,7 +703,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 38. Consider a generator function that generates 10 integers and use it to build an array (★☆☆) (suggestion: np.fromiter)" + "#### 38. Consider a generator function that generates 10 integers and use it to build an array (★☆☆) \n", + "##### (hint: np.fromiter)" ] }, { @@ -684,7 +720,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 39. Create a vector of size 10 with values ranging from 0 to 1, both excluded (★★☆) (suggestion: np.linespace)" + "#### 39. Create a vector of size 10 with values ranging from 0 to 1, both excluded (★★☆) \n", + "##### (hint: np.linespace)" ] }, { @@ -700,7 +737,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 40. Create a random vector of size 10 and sort it (★★☆) (suggestion: sort)" + "#### 40. Create a random vector of size 10 and sort it (★★☆) \n", + "##### (hint: sort)" ] }, { @@ -716,7 +754,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 41. How to sum a small array faster than np.sum? (★★☆) (suggestion: np.add.reduce)" + "#### 41. How to sum a small array faster than np.sum? (★★☆) \n", + "##### (hint: np.add.reduce)" ] }, { @@ -732,7 +771,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 42. Consider two random array A and B, check if they are equal (★★☆) (suggestion: np.allclose, np.array\\_equal)" + "#### 42. Consider two random array A and B, check if they are equal (★★☆) \n", + "##### (hint: np.allclose, np.array\\_equal)" ] }, { @@ -748,7 +788,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 43. Make an array immutable (read-only) (★★☆) (suggestion: flags.writeable)" + "#### 43. Make an array immutable (read-only) (★★☆) \n", + "##### (hint: flags.writeable)" ] }, { @@ -764,7 +805,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 44. Consider a random 10x2 matrix representing cartesian coordinates, convert them to polar coordinates (★★☆) (suggestion: np.sqrt, np.arctan2)" + "#### 44. Consider a random 10x2 matrix representing cartesian coordinates, convert them to polar coordinates (★★☆) \n", + "##### (hint: np.sqrt, np.arctan2)" ] }, { @@ -780,7 +822,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 45. Create random vector of size 10 and replace the maximum value by 0 (★★☆) (suggestion: argmax)" + "#### 45. Create random vector of size 10 and replace the maximum value by 0 (★★☆) \n", + "##### (hint: argmax)" ] }, { @@ -796,7 +839,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 46. Create a structured array with `x` and `y` coordinates covering the \\[0,1\\]x\\[0,1\\] area (★★☆) (suggestion: np.meshgrid)" + "#### 46. Create a structured array with `x` and `y` coordinates covering the \\[0,1\\]x\\[0,1\\] area (★★☆) \n", + "##### (hint: np.meshgrid)" ] }, { @@ -812,7 +856,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 47. Given two arrays, X and Y, construct the Cauchy matrix C (Cij =1/(xi - yj)) (suggestion: np.subtract.outer)" + "#### 47. Given two arrays, X and Y, construct the Cauchy matrix C (Cij =1/(xi - yj)) \n", + "##### (hint: np.subtract.outer)" ] }, { @@ -828,7 +873,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 48. Print the minimum and maximum representable value for each numpy scalar type (★★☆) (suggestion: np.iinfo, np.finfo, eps)" + "#### 48. Print the minimum and maximum representable value for each numpy scalar type (★★☆) \n", + "##### (hint: np.iinfo, np.finfo, eps)" ] }, { @@ -844,7 +890,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 49. How to print all the values of an array? (★★☆) (suggestion: np.set\\_printoptions)" + "#### 49. How to print all the values of an array? (★★☆) \n", + "##### (hint: np.set\\_printoptions)" ] }, { @@ -860,7 +907,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 50. How to find the closest value (to a given scalar) in a vector? (★★☆) (suggestion: argmin)" + "#### 50. How to find the closest value (to a given scalar) in a vector? (★★☆) \n", + "##### (hint: argmin)" ] }, { @@ -876,7 +924,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 51. Create a structured array representing a position (x,y) and a color (r,g,b) (★★☆) (suggestion: dtype)" + "#### 51. Create a structured array representing a position (x,y) and a color (r,g,b) (★★☆) \n", + "##### (hint: dtype)" ] }, { @@ -892,7 +941,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 52. Consider a random vector with shape (100,2) representing coordinates, find point by point distances (★★☆) (suggestion: np.atleast\\_2d, T, np.sqrt)" + "#### 52. Consider a random vector with shape (100,2) representing coordinates, find point by point distances (★★☆) \n", + "##### (hint: np.atleast\\_2d, T, np.sqrt)" ] }, { @@ -908,7 +958,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 53. How to convert a float (32 bits) array into an integer (32 bits) in place? (suggestion: astype(copy=False))" + "#### 53. How to convert a float (32 bits) array into an integer (32 bits) in place? \n", + "##### (hint: astype(copy=False))" ] }, { @@ -924,7 +975,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 54. How to read the following file? (★★☆) (suggestion: np.genfromtxt)" + "#### 54. How to read the following file? (★★☆) \n", + "##### (hint: np.genfromtxt)" ] }, { @@ -951,7 +1003,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 55. What is the equivalent of enumerate for numpy arrays? (★★☆) (suggestion: np.ndenumerate, np.ndindex)" + "#### 55. What is the equivalent of enumerate for numpy arrays? (★★☆) \n", + "##### (hint: np.ndenumerate, np.ndindex)" ] }, { @@ -967,7 +1020,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 56. Generate a generic 2D Gaussian-like array (★★☆) (suggestion: np.meshgrid, np.exp)" + "#### 56. Generate a generic 2D Gaussian-like array (★★☆) \n", + "##### (hint: np.meshgrid, np.exp)" ] }, { @@ -983,7 +1037,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 57. How to randomly place p elements in a 2D array? (★★☆) (suggestion: np.put, np.random.choice)" + "#### 57. How to randomly place p elements in a 2D array? (★★☆) \n", + "##### (hint: np.put, np.random.choice)" ] }, { @@ -999,7 +1054,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 58. Subtract the mean of each row of a matrix (★★☆) (suggestion: mean(axis=,keepdims=))" + "#### 58. Subtract the mean of each row of a matrix (★★☆) \n", + "##### (hint: mean(axis=,keepdims=))" ] }, { @@ -1015,7 +1071,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 59. How to sort an array by the nth column? (★★☆) (suggestion: argsort)" + "#### 59. How to sort an array by the nth column? (★★☆) \n", + "##### (hint: argsort)" ] }, { @@ -1031,7 +1088,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 60. How to tell if a given 2D array has null columns? (★★☆) (suggestion: any, ~)" + "#### 60. How to tell if a given 2D array has null columns? (★★☆) \n", + "##### (hint: any, ~)" ] }, { @@ -1047,7 +1105,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 61. Find the nearest value from a given value in an array (★★☆) (suggestion: np.abs, argmin, flat)" + "#### 61. Find the nearest value from a given value in an array (★★☆) \n", + "##### (hint: np.abs, argmin, flat)" ] }, { @@ -1063,7 +1122,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 62. Considering two arrays with shape (1,3) and (3,1), how to compute their sum using an iterator? (★★☆) (suggestion: np.nditer)" + "#### 62. Considering two arrays with shape (1,3) and (3,1), how to compute their sum using an iterator? (★★☆) \n", + "##### (hint: np.nditer)" ] }, { @@ -1079,7 +1139,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 63. Create an array class that has a name attribute (★★☆) (suggestion: class method)" + "#### 63. Create an array class that has a name attribute (★★☆) \n", + "##### (hint: class method)" ] }, { @@ -1095,7 +1156,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 64. Consider a given vector, how to add 1 to each element indexed by a second vector (be careful with repeated indices)? (★★★) (suggestion: np.bincount | np.add.at)" + "#### 64. Consider a given vector, how to add 1 to each element indexed by a second vector (be careful with repeated indices)? (★★★) \n", + "##### (hint: np.bincount | np.add.at)" ] }, { @@ -1111,7 +1173,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 65. How to accumulate elements of a vector (X) to an array (F) based on an index list (I)? (★★★) (suggestion: np.bincount)" + "#### 65. How to accumulate elements of a vector (X) to an array (F) based on an index list (I)? (★★★) \n", + "##### (hint: np.bincount)" ] }, { @@ -1127,7 +1190,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 66. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique colors (★★★) (suggestion: np.unique)" + "#### 66. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique colors (★★★) \n", + "##### (hint: np.unique)" ] }, { @@ -1143,7 +1207,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 67. Considering a four dimensions array, how to get sum over the last two axis at once? (★★★) (suggestion: sum(axis=(-2,-1)))" + "#### 67. Considering a four dimensions array, how to get sum over the last two axis at once? (★★★) \n", + "##### (hint: sum(axis=(-2,-1)))" ] }, { @@ -1159,7 +1224,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 68. Considering a one-dimensional vector D, how to compute means of subsets of D using a vector S of same size describing subset indices? (★★★) (suggestion: np.bincount)" + "#### 68. Considering a one-dimensional vector D, how to compute means of subsets of D using a vector S of same size describing subset indices? (★★★) \n", + "##### (hint: np.bincount)" ] }, { @@ -1175,7 +1241,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 69. How to get the diagonal of a dot product? (★★★) (suggestion: np.diag)" + "#### 69. How to get the diagonal of a dot product? (★★★) \n", + "##### (hint: np.diag)" ] }, { @@ -1191,7 +1258,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 70. Consider the vector \\[1, 2, 3, 4, 5\\], how to build a new vector with 3 consecutive zeros interleaved between each value? (★★★) (suggestion: array\\[::4\\])" + "#### 70. Consider the vector \\[1, 2, 3, 4, 5\\], how to build a new vector with 3 consecutive zeros interleaved between each value? (★★★) \n", + "##### (hint: array\\[::4\\])" ] }, { @@ -1207,7 +1275,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 71. Consider an array of dimension (5,5,3), how to mulitply it by an array with dimensions (5,5)? (★★★) (suggestion: array\\[:, :, None\\])" + "#### 71. Consider an array of dimension (5,5,3), how to mulitply it by an array with dimensions (5,5)? (★★★) \n", + "##### (hint: array\\[:, :, None\\])" ] }, { @@ -1223,7 +1292,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 72. How to swap two rows of an array? (★★★) (suggestion: array\\[\\[\\]\\] = array\\[\\[\\]\\])" + "#### 72. How to swap two rows of an array? (★★★) \n", + "##### (hint: array\\[\\[\\]\\] = array\\[\\[\\]\\])" ] }, { @@ -1239,7 +1309,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 73. Consider a set of 10 triplets describing 10 triangles (with shared vertices), find the set of unique line segments composing all the triangles (★★★) (suggestion: repeat, np.roll, np.sort, view, np.unique)" + "#### 73. Consider a set of 10 triplets describing 10 triangles (with shared vertices), find the set of unique line segments composing all the triangles (★★★) \n", + "##### (hint: repeat, np.roll, np.sort, view, np.unique)" ] }, { @@ -1255,7 +1326,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 74. Given an array C that is a bincount, how to produce an array A such that np.bincount(A) == C? (★★★) (suggestion: np.repeat)" + "#### 74. Given an array C that is a bincount, how to produce an array A such that np.bincount(A) == C? (★★★) \n", + "##### (hint: np.repeat)" ] }, { @@ -1271,7 +1343,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 75. How to compute averages using a sliding window over an array? (★★★) (suggestion: np.cumsum)" + "#### 75. How to compute averages using a sliding window over an array? (★★★) \n", + "##### (hint: np.cumsum)" ] }, { @@ -1287,7 +1360,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 76. Consider a one-dimensional array Z, build a two-dimensional array whose first row is (Z\\[0\\],Z\\[1\\],Z\\[2\\]) and each subsequent row is shifted by 1 (last row should be (Z\\[-3\\],Z\\[-2\\],Z\\[-1\\]) (★★★) (suggestion: from numpy.lib import stride_tricks)" + "#### 76. Consider a one-dimensional array Z, build a two-dimensional array whose first row is (Z\\[0\\],Z\\[1\\],Z\\[2\\]) and each subsequent row is shifted by 1 (last row should be (Z\\[-3\\],Z\\[-2\\],Z\\[-1\\]) (★★★) \n", + "##### (hint: from numpy.lib import stride_tricks)" ] }, { @@ -1303,7 +1377,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 77. How to negate a boolean, or to change the sign of a float inplace? (★★★) (suggestion: np.logical_not, np.negative)" + "#### 77. How to negate a boolean, or to change the sign of a float inplace? (★★★) \n", + "##### (hint: np.logical_not, np.negative)" ] }, { @@ -1351,7 +1426,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 80. Consider an arbitrary array, write a function that extract a subpart with a fixed shape and centered on a given element (pad with a `fill` value when necessary) (★★★) (suggestion: minimum, maximum)" + "#### 80. Consider an arbitrary array, write a function that extract a subpart with a fixed shape and centered on a given element (pad with a `fill` value when necessary) (★★★) \n", + "##### (hint: minimum, maximum)" ] }, { @@ -1367,7 +1443,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 81. Consider an array Z = \\[1,2,3,4,5,6,7,8,9,10,11,12,13,14\\], how to generate an array R = \\[\\[1,2,3,4\\], \\[2,3,4,5\\], \\[3,4,5,6\\], ..., \\[11,12,13,14\\]\\]? (★★★) (suggestion: stride\\_tricks.as\\_strided)" + "#### 81. Consider an array Z = \\[1,2,3,4,5,6,7,8,9,10,11,12,13,14\\], how to generate an array R = \\[\\[1,2,3,4\\], \\[2,3,4,5\\], \\[3,4,5,6\\], ..., \\[11,12,13,14\\]\\]? (★★★) \n", + "##### (hint: stride\\_tricks.as\\_strided)" ] }, { @@ -1383,7 +1460,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 82. Compute a matrix rank (★★★) (suggestion: np.linalg.svd) (suggestion: np.linalg.svd)" + "#### 82. Compute a matrix rank (★★★) \n", + "##### (hint: np.linalg.svd) (suggestion: np.linalg.svd)" ] }, { @@ -1399,7 +1477,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 83. How to find the most frequent value in an array? (suggestion: np.bincount, argmax)" + "#### 83. How to find the most frequent value in an array? \n", + "##### (hint: np.bincount, argmax)" ] }, { @@ -1415,7 +1494,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 84. Extract all the contiguous 3x3 blocks from a random 10x10 matrix (★★★) (suggestion: stride\\_tricks.as\\_strided)" + "#### 84. Extract all the contiguous 3x3 blocks from a random 10x10 matrix (★★★) \n", + "##### (hint: stride\\_tricks.as\\_strided)" ] }, { @@ -1431,7 +1511,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 85. Create a 2D array subclass such that Z\\[i,j\\] == Z\\[j,i\\] (★★★) (suggestion: class method)" + "#### 85. Create a 2D array subclass such that Z\\[i,j\\] == Z\\[j,i\\] (★★★) \n", + "##### (hint: class method)" ] }, { @@ -1447,7 +1528,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 86. Consider a set of p matrices wich shape (n,n) and a set of p vectors with shape (n,1). How to compute the sum of of the p matrix products at once? (result has shape (n,1)) (★★★) (suggestion: np.tensordot)" + "#### 86. Consider a set of p matrices wich shape (n,n) and a set of p vectors with shape (n,1). How to compute the sum of of the p matrix products at once? (result has shape (n,1)) (★★★) \n", + "##### (hint: np.tensordot)" ] }, { @@ -1463,7 +1545,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 87. Consider a 16x16 array, how to get the block-sum (block size is 4x4)? (★★★) (suggestion: np.add.reduceat)" + "#### 87. Consider a 16x16 array, how to get the block-sum (block size is 4x4)? (★★★) \n", + "##### (hint: np.add.reduceat)" ] }, { @@ -1495,7 +1578,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 89. How to get the n largest values of an array (★★★) (suggestion: np.argsort | np.argpartition)" + "#### 89. How to get the n largest values of an array (★★★) \n", + "##### (hint: np.argsort | np.argpartition)" ] }, { @@ -1511,7 +1595,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 90. Given an arbitrary number of vectors, build the cartesian product (every combinations of every item) (★★★) (suggestion: np.indices)" + "#### 90. Given an arbitrary number of vectors, build the cartesian product (every combinations of every item) (★★★) \n", + "##### (hint: np.indices)" ] }, { @@ -1528,7 +1613,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 91. How to create a record array from a regular array? (★★★) (suggestion: np.core.records.fromarrays)" + "#### 91. How to create a record array from a regular array? (★★★) \n", + "##### (hint: np.core.records.fromarrays)" ] }, { @@ -1544,7 +1630,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 92. Consider a large vector Z, compute Z to the power of 3 using 3 different methods (★★★) (suggestion: np.power, \\*, np.einsum)" + "#### 92. Consider a large vector Z, compute Z to the power of 3 using 3 different methods (★★★) \n", + "##### (hint: np.power, \\*, np.einsum)" ] }, { @@ -1560,7 +1647,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 93. Consider two arrays A and B of shape (8,3) and (2,2). How to find rows of A that contain elements of each row of B regardless of the order of the elements in B? (★★★) (suggestion: np.where)" + "#### 93. Consider two arrays A and B of shape (8,3) and (2,2). How to find rows of A that contain elements of each row of B regardless of the order of the elements in B? (★★★) \n", + "##### (hint: np.where)" ] }, { @@ -1592,7 +1680,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 95. Convert a vector of ints into a matrix binary representation (★★★) (suggestion: np.unpackbits)" + "#### 95. Convert a vector of ints into a matrix binary representation (★★★) \n", + "##### (hint: np.unpackbits)" ] }, { @@ -1608,7 +1697,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 96. Given a two dimensional array, how to extract unique rows? (★★★) (suggestion: np.ascontiguousarray)" + "#### 96. Given a two dimensional array, how to extract unique rows? (★★★) \n", + "##### (hint: np.ascontiguousarray)" ] }, { @@ -1624,7 +1714,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 97. Considering 2 vectors A & B, write the einsum equivalent of inner, outer, sum, and mul function (★★★) (suggestion: np.einsum)" + "#### 97. Considering 2 vectors A & B, write the einsum equivalent of inner, outer, sum, and mul function (★★★) \n", + "##### (hint: np.einsum)" ] }, { @@ -1640,7 +1731,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 98. Considering a path described by two vectors (X,Y), how to sample it using equidistant samples (★★★)? (suggestion: np.cumsum, np.interp)" + "#### 98. Considering a path described by two vectors (X,Y), how to sample it using equidistant samples (★★★)? \n", + "##### (hint: np.cumsum, np.interp)" ] }, { @@ -1656,7 +1748,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 99. Given an integer n and a 2D array X, select from X the rows which can be interpreted as draws from a multinomial distribution with n degrees, i.e., the rows which only contain integers and which sum to n. (★★★) (suggestion: np.logical\\_and.reduce, np.mod)" + "#### 99. Given an integer n and a 2D array X, select from X the rows which can be interpreted as draws from a multinomial distribution with n degrees, i.e., the rows which only contain integers and which sum to n. (★★★) \n", + "##### (hint: np.logical\\_and.reduce, np.mod)" ] }, { @@ -1672,7 +1765,8 @@ "cell_type": "markdown", "metadata": {}, "source": [ - "#### 100. Compute bootstrapped 95% confidence intervals for the mean of a 1D array X (i.e., resample the elements of an array with replacement N times, compute the mean of each sample, and then compute percentiles over the means). (★★★) (suggestion: np.percentile)" + "#### 100. Compute bootstrapped 95% confidence intervals for the mean of a 1D array X (i.e., resample the elements of an array with replacement N times, compute the mean of each sample, and then compute percentiles over the means). (★★★) \n", + "##### (hint: np.percentile)" ] }, { diff --git a/100 Numpy exercises with suggestion.md b/100 Numpy exercises with hint.md similarity index 56% rename from 100 Numpy exercises with suggestion.md rename to 100 Numpy exercises with hint.md index b2a969b..3c10d89 100644 --- a/100 Numpy exercises with suggestion.md +++ b/100 Numpy exercises with hint.md @@ -1,5 +1,5 @@ -# 100 numpy exercises with suggestion +# 100 numpy exercises with hint This is a collection of exercises that have been collected in the numpy mailing list, on stack overflow and in the numpy documentation. I've also created some @@ -10,71 +10,105 @@ those who teach. If you find an error or think you've a better way to solve some of them, feel free to open an issue at -#### 1. Import the numpy package under the name `np` (★☆☆) (suggestion: import … as ..) +#### 1. Import the numpy package under the name `np` (★☆☆) + +##### (hint: import … as ..) -#### 2. Print the numpy version and the configuration (★☆☆) (suggestion: np.\_\_verison\_\_, np.show\_config) +#### 2. Print the numpy version and the configuration (★☆☆) + +##### (hint: np.\_\_verison\_\_, np.show\_config) -#### 3. Create a null vector of size 10 (★☆☆) (suggestion: np.zeros) +#### 3. Create a null vector of size 10 (★☆☆) + +##### (hint: np.zeros) -#### 4. How to find the memory size of any array (★☆☆) (suggestion: size, itemsize) +#### 4. How to find the memory size of any array (★☆☆) + +##### (hint: size, itemsize) -#### 5. How to get the documentation of the numpy add function from the command line? (★☆☆) (suggestion: np.info) +#### 5. How to get the documentation of the numpy add function from the command line? (★☆☆) + +##### (hint: np.info) -#### 6. Create a null vector of size 10 but the fifth value which is 1 (★☆☆) (suggestion: array\[4\]) +#### 6. Create a null vector of size 10 but the fifth value which is 1 (★☆☆) + +##### (hint: array\[4\]) -#### 7. Create a vector with values ranging from 10 to 49 (★☆☆) (suggestion: np.arange) +#### 7. Create a vector with values ranging from 10 to 49 (★☆☆) + +##### (hint: np.arange) -#### 8. Reverse a vector (first element becomes last) (★☆☆) (suggestion: array\[::-1\]) +#### 8. Reverse a vector (first element becomes last) (★☆☆) + +##### (hint: array\[::-1\]) -#### 9. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆) (suggestion: reshape) +#### 9. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆) + +##### (hint: reshape) -#### 10. Find indices of non-zero elements from \[1,2,0,0,4,0\] (★☆☆) (suggestion: np.nonzero) +#### 10. Find indices of non-zero elements from \[1,2,0,0,4,0\] (★☆☆) + +##### (hint: np.nonzero) -#### 11. Create a 3x3 identity matrix (★☆☆) (suggestion: np.eye) +#### 11. Create a 3x3 identity matrix (★☆☆) + +##### (hint: np.eye) -#### 12. Create a 3x3x3 array with random values (★☆☆) (suggestion: np.random.random) +#### 12. Create a 3x3x3 array with random values (★☆☆) + +##### (hint: np.random.random) -#### 13. Create a 10x10 array with random values and find the minimum and maximum values (★☆☆) (suggestion: min, max) +#### 13. Create a 10x10 array with random values and find the minimum and maximum values (★☆☆) + +##### (hint: min, max) -#### 14. Create a random vector of size 30 and find the mean value (★☆☆) (suggestion: mean) +#### 14. Create a random vector of size 30 and find the mean value (★☆☆) + +##### (hint: mean) -#### 15. Create a 2d array with 1 on the border and 0 inside (★☆☆) (suggestion: array\[1:-1, 1:-1\]) +#### 15. Create a 2d array with 1 on the border and 0 inside (★☆☆) + +##### (hint: array\[1:-1, 1:-1\]) -#### 16. How to add a border (filled with 0's) around an existing array? (★☆☆) (suggestion: np.pad) +#### 16. How to add a border (filled with 0's) around an existing array? (★☆☆) + +##### (hint: np.pad) -#### 17. What is the result of the following expression? (★☆☆) (suggestion: NaN = not a number, inf = infinity) +#### 17. What is the result of the following expression? (★☆☆) + +##### (hint: NaN = not a number, inf = infinity) ```python @@ -85,39 +119,57 @@ np.nan - np.nan 0.3 == 3 * 0.1 ``` -#### 18. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆) (suggestion: np.diag) +#### 18. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆) + +##### (hint: np.diag) -#### 19. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆) (suggestion: array\[::2\]) +#### 19. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆) + +##### (hint: array\[::2\]) -#### 20. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element? (suggestion: np.unravel\_index) +#### 20. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element? + +##### (hint: np.unravel\_index) -#### 21. Create a checkerboard 8x8 matrix using the tile function (★☆☆) (suggestion: np.tile) +#### 21. Create a checkerboard 8x8 matrix using the tile function (★☆☆) + +##### (hint: np.tile) -#### 22. Normalize a 5x5 random matrix (★☆☆) (suggestion: (x - min) / (max - min)) +#### 22. Normalize a 5x5 random matrix (★☆☆) + +##### (hint: (x - min) / (max - min)) -#### 23. Create a custom dtype that describes a color as four unsigned bytes (RGBA) (★☆☆) (suggestion: np.dtype) +#### 23. Create a custom dtype that describes a color as four unsigned bytes (RGBA) (★☆☆) + +##### (hint: np.dtype) -#### 24. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆) (suggestion: np.dot | @) +#### 24. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆) + +##### (hint: np.dot | @) -#### 25. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆) (suggestion: >, <=) +#### 25. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆) + +##### (hint: >, <=) -#### 26. What is the output of the following script? (★☆☆) (suggestion: np.sum) +#### 26. What is the output of the following script? (★☆☆) + +##### (hint: np.sum) ```python @@ -149,110 +201,162 @@ np.array(0) // np.array(0) np.array([np.nan]).astype(int).astype(float) ``` -#### 29. How to round away from zero a float array ? (★☆☆) (suggestion: np.uniform, np.copysign, np.ceil, np.abs) +#### 29. How to round away from zero a float array ? (★☆☆) + +##### (hint: np.uniform, np.copysign, np.ceil, np.abs) -#### 30. How to find common values between two arrays? (★☆☆) (suggestion: np.intersect1d) +#### 30. How to find common values between two arrays? (★☆☆) + +##### (hint: np.intersect1d) -#### 31. How to ignore all numpy warnings (not recommended)? (★☆☆) (suggestion: np.seterr, np.errstate) +#### 31. How to ignore all numpy warnings (not recommended)? (★☆☆) + +##### (hint: np.seterr, np.errstate) -#### 32. Is the following expressions true? (★☆☆) (suggestion: imaginary number) +#### 32. Is the following expressions true? (★☆☆) + +##### (hint: imaginary number) ```python np.sqrt(-1) == np.emath.sqrt(-1) ``` -#### 33. How to get the dates of yesterday, today and tomorrow? (★☆☆) (suggestion: np.datetime64, np.timedelta64) +#### 33. How to get the dates of yesterday, today and tomorrow? (★☆☆) + +##### (hint: np.datetime64, np.timedelta64) -#### 34. How to get all the dates corresponding to the month of July 2016? (★★☆) (suggestion: np.arange(dtype=datetime64\['D'\])) +#### 34. How to get all the dates corresponding to the month of July 2016? (★★☆) + +##### (hint: np.arange(dtype=datetime64\['D'\])) -#### 35. How to compute ((A+B)\*(-A/2)) in place (without copy)? (★★☆) (suggestion: np.add(out=), np.negative(out=), np.multiply(out=), np.divide(out=)) +#### 35. How to compute ((A+B)\*(-A/2)) in place (without copy)? (★★☆) + +##### (hint: np.add(out=), np.negative(out=), np.multiply(out=), np.divide(out=)) -#### 36. Extract the integer part of a random array using 5 different methods (★★☆) (suggestion: %, np.floor, np.ceil, astype, np.trunc) +#### 36. Extract the integer part of a random array using 5 different methods (★★☆) + +##### (hint: %, np.floor, np.ceil, astype, np.trunc) -#### 37. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆) (suggestion: np.arange) +#### 37. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆) + +##### (hint: np.arange) -#### 38. Consider a generator function that generates 10 integers and use it to build an array (★☆☆) (suggestion: np.fromiter) +#### 38. Consider a generator function that generates 10 integers and use it to build an array (★☆☆) + +##### (hint: np.fromiter) -#### 39. Create a vector of size 10 with values ranging from 0 to 1, both excluded (★★☆) (suggestion: np.linespace) +#### 39. Create a vector of size 10 with values ranging from 0 to 1, both excluded (★★☆) + +##### (hint: np.linespace) -#### 40. Create a random vector of size 10 and sort it (★★☆) (suggestion: sort) +#### 40. Create a random vector of size 10 and sort it (★★☆) + +##### (hint: sort) -#### 41. How to sum a small array faster than np.sum? (★★☆) (suggestion: np.add.reduce) +#### 41. How to sum a small array faster than np.sum? (★★☆) + +##### (hint: np.add.reduce) -#### 42. Consider two random array A and B, check if they are equal (★★☆) (suggestion: np.allclose, np.array\_equal) +#### 42. Consider two random array A and B, check if they are equal (★★☆) + +##### (hint: np.allclose, np.array\_equal) -#### 43. Make an array immutable (read-only) (★★☆) (suggestion: flags.writeable) +#### 43. Make an array immutable (read-only) (★★☆) + +##### (hint: flags.writeable) -#### 44. Consider a random 10x2 matrix representing cartesian coordinates, convert them to polar coordinates (★★☆) (suggestion: np.sqrt, np.arctan2) +#### 44. Consider a random 10x2 matrix representing cartesian coordinates, convert them to polar coordinates (★★☆) + +##### (hint: np.sqrt, np.arctan2) -#### 45. Create random vector of size 10 and replace the maximum value by 0 (★★☆) (suggestion: argmax) +#### 45. Create random vector of size 10 and replace the maximum value by 0 (★★☆) + +##### (hint: argmax) -#### 46. Create a structured array with `x` and `y` coordinates covering the \[0,1\]x\[0,1\] area (★★☆) (suggestion: np.meshgrid) +#### 46. Create a structured array with `x` and `y` coordinates covering the \[0,1\]x\[0,1\] area (★★☆) + +##### (hint: np.meshgrid) -#### 47. Given two arrays, X and Y, construct the Cauchy matrix C (Cij =1/(xi - yj)) (suggestion: np.subtract.outer) +#### 47. Given two arrays, X and Y, construct the Cauchy matrix C (Cij =1/(xi - yj)) + +##### (hint: np.subtract.outer) -#### 48. Print the minimum and maximum representable value for each numpy scalar type (★★☆) (suggestion: np.iinfo, np.finfo, eps) +#### 48. Print the minimum and maximum representable value for each numpy scalar type (★★☆) + +##### (hint: np.iinfo, np.finfo, eps) -#### 49. How to print all the values of an array? (★★☆) (suggestion: np.set\_printoptions) +#### 49. How to print all the values of an array? (★★☆) + +##### (hint: np.set\_printoptions) -#### 50. How to find the closest value (to a given scalar) in a vector? (★★☆) (suggestion: argmin) +#### 50. How to find the closest value (to a given scalar) in a vector? (★★☆) + +##### (hint: argmin) -#### 51. Create a structured array representing a position (x,y) and a color (r,g,b) (★★☆) (suggestion: dtype) +#### 51. Create a structured array representing a position (x,y) and a color (r,g,b) (★★☆) + +##### (hint: dtype) -#### 52. Consider a random vector with shape (100,2) representing coordinates, find point by point distances (★★☆) (suggestion: np.atleast\_2d, T, np.sqrt) +#### 52. Consider a random vector with shape (100,2) representing coordinates, find point by point distances (★★☆) + +##### (hint: np.atleast\_2d, T, np.sqrt) -#### 53. How to convert a float (32 bits) array into an integer (32 bits) in place? (suggestion: astype(copy=False)) +#### 53. How to convert a float (32 bits) array into an integer (32 bits) in place? + +##### (hint: astype(copy=False)) -#### 54. How to read the following file? (★★☆) (suggestion: np.genfromtxt) +#### 54. How to read the following file? (★★☆) + +##### (hint: np.genfromtxt) ``` @@ -261,95 +365,141 @@ np.sqrt(-1) == np.emath.sqrt(-1) , , 9,10,11 ``` -#### 55. What is the equivalent of enumerate for numpy arrays? (★★☆) (suggestion: np.ndenumerate, np.ndindex) +#### 55. What is the equivalent of enumerate for numpy arrays? (★★☆) +##### (hint: np.ndenumerate, np.ndindex) -#### 56. Generate a generic 2D Gaussian-like array (★★☆) (suggestion: np.meshgrid, np.exp) +#### 56. Generate a generic 2D Gaussian-like array (★★☆) +##### (hint: np.meshgrid, np.exp) -#### 57. How to randomly place p elements in a 2D array? (★★☆) (suggestion: np.put, np.random.choice) +#### 57. How to randomly place p elements in a 2D array? (★★☆) -#### 58. Subtract the mean of each row of a matrix (★★☆) (suggestion: mean(axis=,keepdims=)) +##### (hint: np.put, np.random.choice) -#### 59. How to sort an array by the nth column? (★★☆) (suggestion: argsort) +#### 58. Subtract the mean of each row of a matrix (★★☆) +##### (hint: mean(axis=,keepdims=)) -#### 60. How to tell if a given 2D array has null columns? (★★☆) (suggestion: any, ~) +#### 59. How to sort an array by the nth column? (★★☆) +##### (hint: argsort) -#### 61. Find the nearest value from a given value in an array (★★☆) (suggestion: np.abs, argmin, flat) +#### 60. How to tell if a given 2D array has null columns? (★★☆) -#### 62. Considering two arrays with shape (1,3) and (3,1), how to compute their sum using an iterator? (★★☆) (suggestion: np.nditer) +##### (hint: any, ~) -#### 63. Create an array class that has a name attribute (★★☆) (suggestion: class method) +#### 61. Find the nearest value from a given value in an array (★★☆) +##### (hint: np.abs, argmin, flat) -#### 64. Consider a given vector, how to add 1 to each element indexed by a second vector (be careful with repeated indices)? (★★★) (suggestion: np.bincount | np.add.at) +#### 62. Considering two arrays with shape (1,3) and (3,1), how to compute their sum using an iterator? (★★☆) +##### (hint: np.nditer) -#### 65. How to accumulate elements of a vector (X) to an array (F) based on an index list (I)? (★★★) (suggestion: np.bincount) +#### 63. Create an array class that has a name attribute (★★☆) -#### 66. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique colors (★★★) (suggestion: np.unique) +##### (hint: class method) -#### 67. Considering a four dimensions array, how to get sum over the last two axis at once? (★★★) (suggestion: sum(axis=(-2,-1))) +#### 64. Consider a given vector, how to add 1 to each element indexed by a second vector (be careful with repeated indices)? (★★★) +##### (hint: np.bincount | np.add.at) -#### 68. Considering a one-dimensional vector D, how to compute means of subsets of D using a vector S of same size describing subset indices? (★★★) (suggestion: np.bincount) +#### 65. How to accumulate elements of a vector (X) to an array (F) based on an index list (I)? (★★★) +##### (hint: np.bincount) -#### 69. How to get the diagonal of a dot product? (★★★) (suggestion: np.diag) +#### 66. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique colors (★★★) -#### 70. Consider the vector \[1, 2, 3, 4, 5\], how to build a new vector with 3 consecutive zeros interleaved between each value? (★★★) (suggestion: array\[::4\]) +##### (hint: np.unique) -#### 71. Consider an array of dimension (5,5,3), how to mulitply it by an array with dimensions (5,5)? (★★★) (suggestion: array\[:, :, None\]) +#### 67. Considering a four dimensions array, how to get sum over the last two axis at once? (★★★) +##### (hint: sum(axis=(-2,-1))) -#### 72. How to swap two rows of an array? (★★★) (suggestion: array\[\[\]\] = array\[\[\]\]) +#### 68. Considering a one-dimensional vector D, how to compute means of subsets of D using a vector S of same size describing subset indices? (★★★) +##### (hint: np.bincount) -#### 73. Consider a set of 10 triplets describing 10 triangles (with shared vertices), find the set of unique line segments composing all the triangles (★★★) (suggestion: repeat, np.roll, np.sort, view, np.unique) +#### 69. How to get the diagonal of a dot product? (★★★) -#### 74. Given an array C that is a bincount, how to produce an array A such that np.bincount(A) == C? (★★★) (suggestion: np.repeat) +##### (hint: np.diag) -#### 75. How to compute averages using a sliding window over an array? (★★★) (suggestion: np.cumsum) +#### 70. Consider the vector \[1, 2, 3, 4, 5\], how to build a new vector with 3 consecutive zeros interleaved between each value? (★★★) +##### (hint: array\[::4\]) -#### 76. Consider a one-dimensional array Z, build a two-dimensional array whose first row is (Z\[0\],Z\[1\],Z\[2\]) and each subsequent row is shifted by 1 (last row should be (Z\[-3\],Z\[-2\],Z\[-1\]) (★★★) (suggestion: from numpy.lib import stride\_tricks) +#### 71. Consider an array of dimension (5,5,3), how to mulitply it by an array with dimensions (5,5)? (★★★) +##### (hint: array\[:, :, None\]) -#### 77. How to negate a boolean, or to change the sign of a float inplace? (★★★) (suggestion: np.logical_not, np.negative) + + +#### 72. How to swap two rows of an array? (★★★) + +##### (hint: array\[\[\]\] = array\[\[\]\]) + + + +#### 73. Consider a set of 10 triplets describing 10 triangles (with shared vertices), find the set of unique line segments composing all the triangles (★★★) + +##### (hint: repeat, np.roll, np.sort, view, np.unique) + + + +#### 74. Given an array C that is a bincount, how to produce an array A such that np.bincount(A) == C? (★★★) + +##### (hint: np.repeat) + + + +#### 75. How to compute averages using a sliding window over an array? (★★★) + +##### (hint: np.cumsum) + + + +#### 76. Consider a one-dimensional array Z, build a two-dimensional array whose first row is (Z\[0\],Z\[1\],Z\[2\]) and each subsequent row is shifted by 1 (last row should be (Z\[-3\],Z\[-2\],Z\[-1\]) (★★★) + +##### (hint: from numpy.lib import stride\_tricks) + + + +#### 77. How to negate a boolean, or to change the sign of a float inplace? (★★★) + +##### (hint: np.logical_not, np.negative) @@ -361,35 +511,51 @@ np.sqrt(-1) == np.emath.sqrt(-1) -#### 80. Consider an arbitrary array, write a function that extract a subpart with a fixed shape and centered on a given element (pad with a `fill` value when necessary) (★★★) (suggestion: minimum, maximum) +#### 80. Consider an arbitrary array, write a function that extract a subpart with a fixed shape and centered on a given element (pad with a `fill` value when necessary) (★★★) + +##### (hint: minimum, maximum) -#### 81. Consider an array Z = \[1,2,3,4,5,6,7,8,9,10,11,12,13,14\], how to generate an array R = \[\[1,2,3,4\], \[2,3,4,5\], \[3,4,5,6\], ..., \[11,12,13,14\]\]? (★★★) (suggestion: stride\_tricks.as\_strided) +#### 81. Consider an array Z = \[1,2,3,4,5,6,7,8,9,10,11,12,13,14\], how to generate an array R = \[\[1,2,3,4\], \[2,3,4,5\], \[3,4,5,6\], ..., \[11,12,13,14\]\]? (★★★) + +##### (hint: stride\_tricks.as\_strided) -#### 82. Compute a matrix rank (★★★) (suggestion: np.linalg.svd) +#### 82. Compute a matrix rank (★★★) + +##### (hint: np.linalg.svd) -#### 83. How to find the most frequent value in an array? (suggestion: np.bincount, argmax) +#### 83. How to find the most frequent value in an array? + +##### (hint: np.bincount, argmax) -#### 84. Extract all the contiguous 3x3 blocks from a random 10x10 matrix (★★★) (suggestion: stride\_tricks.as\_strided) +#### 84. Extract all the contiguous 3x3 blocks from a random 10x10 matrix (★★★) + +##### (hint: stride\_tricks.as\_strided) -#### 85. Create a 2D array subclass such that Z\[i,j\] == Z\[j,i\] (★★★) (suggestion: class method) +#### 85. Create a 2D array subclass such that Z\[i,j\] == Z\[j,i\] (★★★) + +##### (hint: class method) -#### 86. Consider a set of p matrices wich shape (n,n) and a set of p vectors with shape (n,1). How to compute the sum of of the p matrix products at once? (result has shape (n,1)) (★★★) (suggestion: np.tensordot) +#### 86. Consider a set of p matrices wich shape (n,n) and a set of p vectors with shape (n,1). How to compute the sum of of the p matrix products at once? (result has shape (n,1)) (★★★) + +##### (hint: np.tensordot) -#### 87. Consider a 16x16 array, how to get the block-sum (block size is 4x4)? (★★★) (suggestion: np.add.reduceat) +#### 87. Consider a 16x16 array, how to get the block-sum (block size is 4x4)? (★★★) + +##### (hint: np.add.reduceat) @@ -397,23 +563,33 @@ np.sqrt(-1) == np.emath.sqrt(-1) -#### 89. How to get the n largest values of an array (★★★) (suggestion: np.argsort | np.argpartition) +#### 89. How to get the n largest values of an array (★★★) + +##### (hint: np.argsort | np.argpartition) -#### 90. Given an arbitrary number of vectors, build the cartesian product (every combinations of every item) (★★★) (suggestion: np.indices) +#### 90. Given an arbitrary number of vectors, build the cartesian product (every combinations of every item) (★★★) + +##### (hint: np.indices) -#### 91. How to create a record array from a regular array? (★★★) (suggestion: np.core.records.fromarrays) +#### 91. How to create a record array from a regular array? (★★★) + +##### (hint: np.core.records.fromarrays) -#### 92. Consider a large vector Z, compute Z to the power of 3 using 3 different methods (★★★) (suggestion: np.power, \*, np.einsum) +#### 92. Consider a large vector Z, compute Z to the power of 3 using 3 different methods (★★★) + +##### (hint: np.power, \*, np.einsum) -#### 93. Consider two arrays A and B of shape (8,3) and (2,2). How to find rows of A that contain elements of each row of B regardless of the order of the elements in B? (★★★) (suggestion: np.where) +#### 93. Consider two arrays A and B of shape (8,3) and (2,2). How to find rows of A that contain elements of each row of B regardless of the order of the elements in B? (★★★) + +##### (hint: np.where) @@ -421,25 +597,37 @@ np.sqrt(-1) == np.emath.sqrt(-1) -#### 95. Convert a vector of ints into a matrix binary representation (★★★) (suggestion: np.unpackbits) +#### 95. Convert a vector of ints into a matrix binary representation (★★★) + +##### (hint: np.unpackbits) -#### 96. Given a two dimensional array, how to extract unique rows? (★★★) (suggestion: np.ascontiguousarray) +#### 96. Given a two dimensional array, how to extract unique rows? (★★★) + +##### (hint: np.ascontiguousarray) -#### 97. Considering 2 vectors A & B, write the einsum equivalent of inner, outer, sum, and mul function (★★★) (suggestion: np.einsum) +#### 97. Considering 2 vectors A & B, write the einsum equivalent of inner, outer, sum, and mul function (★★★) + +##### (hint: np.einsum) -#### 98. Considering a path described by two vectors (X,Y), how to sample it using equidistant samples (★★★)? (suggestion: np.cumsum, np.interp) +#### 98. Considering a path described by two vectors (X,Y), how to sample it using equidistant samples (★★★)? + +##### (hint: np.cumsum, np.interp) -#### 99. Given an integer n and a 2D array X, select from X the rows which can be interpreted as draws from a multinomial distribution with n degrees, i.e., the rows which only contain integers and which sum to n. (★★★) (suggestion: np.logical\_and.reduce, np.mod) +#### 99. Given an integer n and a 2D array X, select from X the rows which can be interpreted as draws from a multinomial distribution with n degrees, i.e., the rows which only contain integers and which sum to n. (★★★) + +##### (hint: np.logical\_and.reduce, np.mod) -#### 100. Compute bootstrapped 95% confidence intervals for the mean of a 1D array X (i.e., resample the elements of an array with replacement N times, compute the mean of each sample, and then compute percentiles over the means). (★★★) (suggestion: np.percentile) +#### 100. Compute bootstrapped 95% confidence intervals for the mean of a 1D array X (i.e., resample the elements of an array with replacement N times, compute the mean of each sample, and then compute percentiles over the means). (★★★) + +##### (hint: np.percentile)