solutions update from a4bf63e

Remove an incorrect solution (fancy indexing) from Numpy exercise No16

100_Numpy_exercises_with_hints_with_solutions.md

@@ -38,6 +38,9 @@ print(Z)
 ```python
 Z = np.zeros((10,10))
 print("%d bytes" % (Z.size * Z.itemsize))
+
+# Simpler alternative
+print("%d bytes" % Z.nbytes)
 ```
 #### 5. How to get the documentation of the numpy add function from the command line? (★☆☆)
 `hint: np.info`
@@ -128,7 +131,7 @@ Z = np.ones((5,5))
 Z = np.pad(Z, pad_width=1, mode='constant', constant_values=0)
 print(Z)
 
-# Using fancy indexing
+# Not a solution to this problem but good to know: using fancy indexing for in-place edit
 Z[:, [0, -1]] = 0
 Z[[0, -1], :] = 0
 print(Z)
@@ -545,7 +548,7 @@ s = StringIO('''1, 2, 3, 4, 5
 
                  ,  , 9,10,11
 ''')
-Z = np.genfromtxt(s, delimiter=",", dtype=np.int)
+Z = np.genfromtxt(s, delimiter=",", dtype = int, filling_values = 0)
 print(Z)
 ```
 #### 55. What is the equivalent of enumerate for numpy arrays? (★★☆)
@@ -993,7 +996,8 @@ print(sliding_window_view(Z, window_shape=4))
 
 Z = np.random.uniform(0,1,(10,10))
 U, S, V = np.linalg.svd(Z) # Singular Value Decomposition
-rank = np.sum(S > 1e-10)
+threshold = len(S) * S.max() * np.finfo(S.dtype).eps
+rank = np.sum(S > threshold)
 print(rank)
 
 # alternative solution:
@@ -1086,11 +1090,8 @@ k = 4
 windows = np.lib.stride_tricks.sliding_window_view(Z, (k, k))
 S = windows[::k, ::k, ...].sum(axis=(-2, -1))
 
-# Author: Jeff Luo (@Jeff1999)
-
-Z = np.ones((16, 16))
-k = 4
-print(sliding_window_view(Z, window_shape=(k, k))[::k, ::k].sum(axis=(-2, -1)))
+# alternative solution (by @Gattocrucco)
+S = Z.reshape(4, 4, 4, 4).sum((1, 3))
 ```
 #### 88. How to implement the Game of Life using numpy arrays? (★★★)
 `No hints provided...`

100_Numpy_exercises_with_solutions.md

@@ -38,6 +38,9 @@ print(Z)
 ```python
 Z = np.zeros((10,10))
 print("%d bytes" % (Z.size * Z.itemsize))
+
+# Simpler alternative
+print("%d bytes" % Z.nbytes)
 ```
 #### 5. How to get the documentation of the numpy add function from the command line? (★☆☆)
 
@@ -128,7 +131,7 @@ Z = np.ones((5,5))
 Z = np.pad(Z, pad_width=1, mode='constant', constant_values=0)
 print(Z)
 
-# Using fancy indexing
+# Not a solution to this problem but good to know: using fancy indexing for in-place edit
 Z[:, [0, -1]] = 0
 Z[[0, -1], :] = 0
 print(Z)
@@ -545,7 +548,7 @@ s = StringIO('''1, 2, 3, 4, 5
 
                  ,  , 9,10,11
 ''')
-Z = np.genfromtxt(s, delimiter=",", dtype=np.int)
+Z = np.genfromtxt(s, delimiter=",", dtype = int, filling_values = 0)
 print(Z)
 ```
 #### 55. What is the equivalent of enumerate for numpy arrays? (★★☆)
@@ -993,7 +996,8 @@ print(sliding_window_view(Z, window_shape=4))
 
 Z = np.random.uniform(0,1,(10,10))
 U, S, V = np.linalg.svd(Z) # Singular Value Decomposition
-rank = np.sum(S > 1e-10)
+threshold = len(S) * S.max() * np.finfo(S.dtype).eps
+rank = np.sum(S > threshold)
 print(rank)
 
 # alternative solution:
@@ -1086,11 +1090,8 @@ k = 4
 windows = np.lib.stride_tricks.sliding_window_view(Z, (k, k))
 S = windows[::k, ::k, ...].sum(axis=(-2, -1))
 
-# Author: Jeff Luo (@Jeff1999)
-
-Z = np.ones((16, 16))
-k = 4
-print(sliding_window_view(Z, window_shape=(k, k))[::k, ::k].sum(axis=(-2, -1)))
+# alternative solution (by @Gattocrucco)
+S = Z.reshape(4, 4, 4, 4).sum((1, 3))
 ```
 #### 88. How to implement the Game of Life using numpy arrays? (★★★)
 

100_Numpy_random.ipynb

@@ -2,7 +2,7 @@
  "cells": [
   {
    "cell_type": "markdown",
-   "id": "738eba3f",
+   "id": "a3747e86",
    "metadata": {},
    "source": [
     "# 100 numpy exercises\n",
@@ -18,7 +18,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "f65f901e",
+   "id": "8b9ef9a4",
    "metadata": {},
    "source": [
     "File automatically generated. See the documentation to update questions/answers/hints programmatically."
@@ -26,17 +26,17 @@
   },
   {
    "cell_type": "markdown",
-   "id": "15045647",
+   "id": "792c1217",
    "metadata": {},
    "source": [
-    "Run the `initialize.py` module, then call a random question with `pick()` an hint towards its solution with\n",
+    "Run the `initialise.py` module, then call a random question with `pick()` an hint towards its solution with\n",
     "`hint(n)` and the answer with `answer(n)`, where n is the number of the picked question."
    ]
   },
   {
    "cell_type": "code",
    "execution_count": null,
-   "id": "0d23aa5b",
+   "id": "541f746c",
    "metadata": {},
    "outputs": [],
    "source": [
@@ -46,7 +46,7 @@
   {
    "cell_type": "code",
    "execution_count": null,
-   "id": "4a6a613b",
+   "id": "d1743adb",
    "metadata": {},
    "outputs": [],
    "source": [

source/exercises100.ktx

@@ -37,6 +37,9 @@ hint: size, itemsize
 Z = np.zeros((10,10))
 print("%d bytes" % (Z.size * Z.itemsize))
 
+# Simpler alternative
+print("%d bytes" % Z.nbytes)
+
 < q5
 How to get the documentation of the numpy add function from the command line? (★☆☆)
 
@@ -162,7 +165,7 @@ Z = np.ones((5,5))
 Z = np.pad(Z, pad_width=1, mode='constant', constant_values=0)
 print(Z)
 
-# Using fancy indexing
+# Not a solution to this problem but good to know: using fancy indexing for in-place edit
 Z[:, [0, -1]] = 0
 Z[[0, -1], :] = 0
 print(Z)
@@ -693,7 +696,7 @@ s = StringIO('''1, 2, 3, 4, 5
 
                  ,  , 9,10,11
 ''')
-Z = np.genfromtxt(s, delimiter=",", dtype=np.int)
+Z = np.genfromtxt(s, delimiter=",", dtype = int, filling_values = 0)
 print(Z)
 
 < q55
@@ -1225,7 +1228,8 @@ hint: np.linalg.svd, np.linalg.matrix_rank
 
 Z = np.random.uniform(0,1,(10,10))
 U, S, V = np.linalg.svd(Z) # Singular Value Decomposition
-rank = np.sum(S > 1e-10)
+threshold = len(S) * S.max() * np.finfo(S.dtype).eps
+rank = np.sum(S > threshold)
 print(rank)
 
 # alternative solution:
@@ -1333,11 +1337,8 @@ k = 4
 windows = np.lib.stride_tricks.sliding_window_view(Z, (k, k))
 S = windows[::k, ::k, ...].sum(axis=(-2, -1))
 
-# Author: Jeff Luo (@Jeff1999)
-
-Z = np.ones((16, 16))
-k = 4
-print(sliding_window_view(Z, window_shape=(k, k))[::k, ::k].sum(axis=(-2, -1)))
+# alternative solution (by @Gattocrucco)
+S = Z.reshape(4, 4, 4, 4).sum((1, 3))
 
 < q88
 How to implement the Game of Life using numpy arrays? (★★★)