daviddoji/numpy-100
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Added some exercises

Browse Source
This commit is contained in:
Nicolas P. Rougier
2016-07-14 11:55:31 -05:00
parent 26f1f77460
commit 03ccfbdd33
2 changed files with 234 additions and 87 deletions
Download Patch File Download Diff File Expand all files Collapse all files

91
README.html
View File

@@ -4,12 +4,12 @@
<head> <head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="generator" content="Docutils 0.12: http://docutils.sourceforge.net/" /> <meta name="generator" content="Docutils 0.12: http://docutils.sourceforge.net/" />
<title>100 numpy exercises</title> <title>100 numpy exercises</title>
<link rel="stylesheet" href="numpy.css" type="text/css" /> <link rel="stylesheet" href="numpy.css" type="text/css" />
</head> </head>
<body> <body>
<div class="document" id="numpy-exercises"> <div class="document" id="numpy-exercises">
<h1 class="title">100 numpy exercises</h1> <h1 class="title">100 numpy exercises</h1>
<h2 class="subtitle" id="a-joint-effort-of-the-numpy-community">A joint effort of the numpy community</h2> <h2 class="subtitle" id="a-joint-effort-of-the-numpy-community">A joint effort of the numpy community</h2>
<p>The goal is both to offer a quick reference for new and old users and to <p>The goal is both to offer a quick reference for new and old users and to
@@ -158,6 +158,14 @@ python -c <span class="literal string double">&quot;import numpy; numpy.info(num
<span class="keyword">print</span><span class="punctuation">(</span><span class="name">Z</span><span class="punctuation">)</span> <span class="keyword">print</span><span class="punctuation">(</span><span class="name">Z</span><span class="punctuation">)</span>
</pre> </pre>
</li> </li>
<li><p class="first">Create a custom dtype that describes a color as four unisgned bytes (RGBA) (★☆☆)</p>
<pre class="code python literal-block">
<span class="name">color</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">dtype</span><span class="punctuation">([(</span><span class="literal string double">&quot;r&quot;</span><span class="punctuation">,</span> <span class="name">np</span><span class="operator">.</span><span class="name">ubyte</span><span class="punctuation">,</span> <span class="literal number integer">1</span><span class="punctuation">),</span>
<span class="punctuation">(</span><span class="literal string double">&quot;g&quot;</span><span class="punctuation">,</span> <span class="name">np</span><span class="operator">.</span><span class="name">ubyte</span><span class="punctuation">,</span> <span class="literal number integer">1</span><span class="punctuation">),</span>
<span class="punctuation">(</span><span class="literal string double">&quot;b&quot;</span><span class="punctuation">,</span> <span class="name">np</span><span class="operator">.</span><span class="name">ubyte</span><span class="punctuation">,</span> <span class="literal number integer">1</span><span class="punctuation">),</span>
<span class="punctuation">(</span><span class="literal string double">&quot;a&quot;</span><span class="punctuation">,</span> <span class="name">np</span><span class="operator">.</span><span class="name">ubyte</span><span class="punctuation">,</span> <span class="literal number integer">1</span><span class="punctuation">)])</span>
</pre>
</li>
<li><p class="first">Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆)</p> <li><p class="first">Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆)</p>
<pre class="code python literal-block"> <pre class="code python literal-block">
<span class="name">Z</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">dot</span><span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">ones</span><span class="punctuation">((</span><span class="literal number integer">5</span><span class="punctuation">,</span><span class="literal number integer">3</span><span class="punctuation">)),</span> <span class="name">np</span><span class="operator">.</span><span class="name">ones</span><span class="punctuation">((</span><span class="literal number integer">3</span><span class="punctuation">,</span><span class="literal number integer">2</span><span class="punctuation">)))</span> <span class="name">Z</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">dot</span><span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">ones</span><span class="punctuation">((</span><span class="literal number integer">5</span><span class="punctuation">,</span><span class="literal number integer">3</span><span class="punctuation">)),</span> <span class="name">np</span><span class="operator">.</span><span class="name">ones</span><span class="punctuation">((</span><span class="literal number integer">3</span><span class="punctuation">,</span><span class="literal number integer">2</span><span class="punctuation">)))</span>
@@ -172,6 +180,53 @@ python -c <span class="literal string double">&quot;import numpy; numpy.info(num
<span class="name">Z</span><span class="punctuation">[(</span><span class="literal number integer">3</span> <span class="operator">&lt;</span> <span class="name">Z</span><span class="punctuation">)</span> <span class="operator">&amp;</span> <span class="punctuation">(</span><span class="name">Z</span> <span class="operator">&lt;=</span> <span class="literal number integer">8</span><span class="punctuation">)]</span> <span class="operator">*=</span> <span class="operator">-</span><span class="literal number integer">1</span> <span class="name">Z</span><span class="punctuation">[(</span><span class="literal number integer">3</span> <span class="operator">&lt;</span> <span class="name">Z</span><span class="punctuation">)</span> <span class="operator">&amp;</span> <span class="punctuation">(</span><span class="name">Z</span> <span class="operator">&lt;=</span> <span class="literal number integer">8</span><span class="punctuation">)]</span> <span class="operator">*=</span> <span class="operator">-</span><span class="literal number integer">1</span>
</pre> </pre>
</li> </li>
<li><p class="first">What is the output of the following script? (★☆☆)</p>
<pre class="code python literal-block">
<span class="comment single"># Author: Jake VanderPlas</span>
<span class="keyword">print</span><span class="punctuation">(</span><span class="name builtin">sum</span><span class="punctuation">(</span><span class="name builtin">range</span><span class="punctuation">(</span><span class="literal number integer">5</span><span class="punctuation">),</span><span class="operator">-</span><span class="literal number integer">1</span><span class="punctuation">))</span>
<span class="keyword namespace">from</span> <span class="name namespace">numpy</span> <span class="keyword namespace">import</span> <span class="operator">*</span>
<span class="keyword">print</span><span class="punctuation">(</span><span class="name builtin">sum</span><span class="punctuation">(</span><span class="name builtin">range</span><span class="punctuation">(</span><span class="literal number integer">5</span><span class="punctuation">),</span><span class="operator">-</span><span class="literal number integer">1</span><span class="punctuation">))</span>
</pre>
</li>
<li><p class="first">Consider an integer vector Z, which of these expressions are legal? (★☆☆)</p>
<pre class="code python literal-block">
<span class="name">Z</span><span class="operator">**</span><span class="name">Z</span>
<span class="literal number integer">2</span> <span class="operator">&lt;&lt;</span> <span class="name">Z</span> <span class="operator">&gt;&gt;</span> <span class="literal number integer">2</span>
<span class="name">Z</span> <span class="operator">&lt;-</span> <span class="name">Z</span>
<span class="literal number integer">1j</span><span class="operator">*</span><span class="name">Z</span>
<span class="name">Z</span><span class="operator">/</span><span class="literal number integer">1</span><span class="operator">/</span><span class="literal number integer">1</span>
<span class="name">Z</span><span class="operator">&lt;</span><span class="name">Z</span><span class="operator">&gt;</span><span class="name">Z</span>
</pre>
</li>
<li><p class="first">What are the result of the following expressions?</p>
<pre class="code python literal-block">
<span class="name">np</span><span class="operator">.</span><span class="name">array</span><span class="punctuation">(</span><span class="literal number integer">0</span><span class="punctuation">)</span> <span class="operator">//</span> <span class="name">np</span><span class="operator">.</span><span class="name">array</span><span class="punctuation">(</span><span class="literal number integer">0</span><span class="punctuation">)</span>
<span class="name">np</span><span class="operator">.</span><span class="name">array</span><span class="punctuation">(</span><span class="literal number integer">0</span><span class="punctuation">)</span> <span class="operator">//</span> <span class="name">np</span><span class="operator">.</span><span class="name">array</span><span class="punctuation">(</span><span class="literal number float">0.</span><span class="punctuation">)</span>
<span class="name">np</span><span class="operator">.</span><span class="name">array</span><span class="punctuation">(</span><span class="literal number integer">0</span><span class="punctuation">)</span> <span class="operator">/</span> <span class="name">np</span><span class="operator">.</span><span class="name">array</span><span class="punctuation">(</span><span class="literal number integer">0</span><span class="punctuation">)</span>
<span class="name">np</span><span class="operator">.</span><span class="name">array</span><span class="punctuation">(</span><span class="literal number integer">0</span><span class="punctuation">)</span> <span class="operator">/</span> <span class="name">np</span><span class="operator">.</span><span class="name">array</span><span class="punctuation">(</span><span class="literal number float">0.</span><span class="punctuation">)</span>
</pre>
</li>
<li><p class="first">How to round away from zero a float array ? (★☆☆)</p>
<pre class="code python literal-block">
<span class="comment single"># Author: Charles R Harris</span>
<span class="name">Z</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">random</span><span class="operator">.</span><span class="name">uniform</span><span class="punctuation">(</span><span class="operator">-</span><span class="literal number integer">10</span><span class="punctuation">,</span><span class="operator">+</span><span class="literal number integer">10</span><span class="punctuation">,</span><span class="literal number integer">10</span><span class="punctuation">)</span>
<span class="keyword">print</span> <span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">trunc</span><span class="punctuation">(</span><span class="name">Z</span> <span class="operator">+</span> <span class="name">np</span><span class="operator">.</span><span class="name">copysign</span><span class="punctuation">(</span><span class="literal number float">0.5</span><span class="punctuation">,</span> <span class="name">Z</span><span class="punctuation">)))</span>
</pre>
</li>
<li><p class="first">Extract the integer part of a random array using 5 different methods (★★☆)</p>
<pre class="code python literal-block">
<span class="name">Z</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">random</span><span class="operator">.</span><span class="name">uniform</span><span class="punctuation">(</span><span class="literal number integer">0</span><span class="punctuation">,</span><span class="literal number integer">10</span><span class="punctuation">,</span><span class="literal number integer">10</span><span class="punctuation">)</span>
<span class="keyword">print</span> <span class="punctuation">(</span><span class="name">Z</span> <span class="operator">-</span> <span class="name">Z</span><span class="operator">%</span><span class="literal number integer">1</span><span class="punctuation">)</span>
<span class="keyword">print</span> <span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">floor</span><span class="punctuation">(</span><span class="name">Z</span><span class="punctuation">))</span>
<span class="keyword">print</span> <span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">ceil</span><span class="punctuation">(</span><span class="name">Z</span><span class="punctuation">)</span><span class="operator">-</span><span class="literal number integer">1</span><span class="punctuation">)</span>
<span class="keyword">print</span> <span class="punctuation">(</span><span class="name">Z</span><span class="operator">.</span><span class="name">astype</span><span class="punctuation">(</span><span class="name builtin">int</span><span class="punctuation">))</span>
<span class="keyword">print</span> <span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">trunc</span><span class="punctuation">(</span><span class="name">Z</span><span class="punctuation">))</span>
</pre>
</li>
<li><p class="first">Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆)</p> <li><p class="first">Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆)</p>
<pre class="code python literal-block"> <pre class="code python literal-block">
<span class="name">Z</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">zeros</span><span class="punctuation">((</span><span class="literal number integer">5</span><span class="punctuation">,</span><span class="literal number integer">5</span><span class="punctuation">))</span> <span class="name">Z</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">zeros</span><span class="punctuation">((</span><span class="literal number integer">5</span><span class="punctuation">,</span><span class="literal number integer">5</span><span class="punctuation">))</span>
@@ -322,14 +377,15 @@ point by point distances (★★☆)</p>
<span class="name">Z</span> <span class="operator">=</span> <span class="name">Z</span><span class="operator">.</span><span class="name">astype</span><span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">float32</span><span class="punctuation">,</span> <span class="name">copy</span><span class="operator">=</span><span class="name builtin pseudo">False</span><span class="punctuation">)</span> <span class="name">Z</span> <span class="operator">=</span> <span class="name">Z</span><span class="operator">.</span><span class="name">astype</span><span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">float32</span><span class="punctuation">,</span> <span class="name">copy</span><span class="operator">=</span><span class="name builtin pseudo">False</span><span class="punctuation">)</span>
</pre> </pre>
</li> </li>
<li><p class="first">Consider the following file:</p> <li><p class="first">How to read the following file? (★★☆)</p>
<pre class="literal-block">
1,2,3,4,5
6,,,7,8
,,9,10,11
</pre>
<p>How to read it ? (★★☆)</p>
<pre class="code python literal-block"> <pre class="code python literal-block">
<span class="comment single"># File content:</span>
<span class="comment single"># -------------</span>
<span class="literal number integer">1</span><span class="punctuation">,</span><span class="literal number integer">2</span><span class="punctuation">,</span><span class="literal number integer">3</span><span class="punctuation">,</span><span class="literal number integer">4</span><span class="punctuation">,</span><span class="literal number integer">5</span>
<span class="literal number integer">6</span><span class="punctuation">,,,</span><span class="literal number integer">7</span><span class="punctuation">,</span><span class="literal number integer">8</span>
<span class="punctuation">,,</span><span class="literal number integer">9</span><span class="punctuation">,</span><span class="literal number integer">10</span><span class="punctuation">,</span><span class="literal number integer">11</span>
<span class="comment single"># -------------</span>
<span class="name">Z</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">genfromtxt</span><span class="punctuation">(</span><span class="literal string double">&quot;missing.dat&quot;</span><span class="punctuation">,</span> <span class="name">delimiter</span><span class="operator">=</span><span class="literal string double">&quot;,&quot;</span><span class="punctuation">)</span> <span class="name">Z</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">genfromtxt</span><span class="punctuation">(</span><span class="literal string double">&quot;missing.dat&quot;</span><span class="punctuation">,</span> <span class="name">delimiter</span><span class="operator">=</span><span class="literal string double">&quot;,&quot;</span><span class="punctuation">)</span>
</pre> </pre>
</li> </li>
@@ -399,6 +455,21 @@ point by point distances (★★☆)</p>
<span class="keyword">print</span><span class="punctuation">(</span><span class="name">m</span><span class="punctuation">)</span> <span class="keyword">print</span><span class="punctuation">(</span><span class="name">m</span><span class="punctuation">)</span>
</pre> </pre>
</li> </li>
<li><p class="first">Create an array class that has a <cite>name</cite> attribute (★★☆)</p>
<pre class="code python literal-block">
<span class="keyword">class</span> <span class="name class">NamedArray</span><span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">ndarray</span><span class="punctuation">):</span>
<span class="keyword">def</span> <span class="name function">__new__</span><span class="punctuation">(</span><span class="name">cls</span><span class="punctuation">,</span> <span class="name">array</span><span class="punctuation">,</span> <span class="name">name</span><span class="operator">=</span><span class="literal string double">&quot;no name&quot;</span><span class="punctuation">):</span>
<span class="name">obj</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">asarray</span><span class="punctuation">(</span><span class="name">array</span><span class="punctuation">)</span><span class="operator">.</span><span class="name">view</span><span class="punctuation">(</span><span class="name">cls</span><span class="punctuation">)</span>
<span class="name">obj</span><span class="operator">.</span><span class="name">name</span> <span class="operator">=</span> <span class="name">name</span>
<span class="keyword">return</span> <span class="name">obj</span>
<span class="keyword">def</span> <span class="name function">__array_finalize__</span><span class="punctuation">(</span><span class="name builtin pseudo">self</span><span class="punctuation">,</span> <span class="name">obj</span><span class="punctuation">):</span>
<span class="keyword">if</span> <span class="name">obj</span> <span class="operator word">is</span> <span class="name builtin pseudo">None</span><span class="punctuation">:</span> <span class="keyword">return</span>
<span class="name builtin pseudo">self</span><span class="operator">.</span><span class="name">info</span> <span class="operator">=</span> <span class="name builtin">getattr</span><span class="punctuation">(</span><span class="name">obj</span><span class="punctuation">,</span> <span class="literal string single">'name'</span><span class="punctuation">,</span> <span class="literal string double">&quot;no name&quot;</span><span class="punctuation">)</span>
<span class="name">Z</span> <span class="operator">=</span> <span class="name">NamedArray</span><span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">arange</span><span class="punctuation">(</span><span class="literal number integer">10</span><span class="punctuation">),</span> <span class="literal string double">&quot;range_10&quot;</span><span class="punctuation">)</span>
<span class="keyword">print</span> <span class="punctuation">(</span><span class="name">Z</span><span class="operator">.</span><span class="name">name</span><span class="punctuation">)</span>
</pre>
</li>
<li><p class="first">Consider a given vector, how to add 1 to each element indexed by a second <li><p class="first">Consider a given vector, how to add 1 to each element indexed by a second
vector (be careful with repeated indices)? (★★★)</p> vector (be careful with repeated indices)? (★★★)</p>
<pre class="code python literal-block"> <pre class="code python literal-block">
@@ -766,7 +837,7 @@ combinations of every item) (★★★)</p>
<span class="name">formats</span> <span class="operator">=</span> <span class="literal string single">'S8, f8, i8'</span><span class="punctuation">)</span> <span class="name">formats</span> <span class="operator">=</span> <span class="literal string single">'S8, f8, i8'</span><span class="punctuation">)</span>
</pre> </pre>
</li> </li>
<li><p class="first">Comsider a large vector Z, compute Z to the power of 3 using 3 different <li><p class="first">Consider a large vector Z, compute Z to the power of 3 using 3 different
methods (★★★)</p> methods (★★★)</p>
<pre class="code python literal-block"> <pre class="code python literal-block">
<span class="name">Author</span><span class="punctuation">:</span> <span class="name">Ryan</span> <span class="name">G</span><span class="operator">.</span> <span class="name">Author</span><span class="punctuation">:</span> <span class="name">Ryan</span> <span class="name">G</span><span class="operator">.</span>

90
README.rst
View File

@@ -193,6 +193,14 @@ Thanks to Michiaki Ariga, there is now a
Z = (Z - Zmin)/(Zmax - Zmin) Z = (Z - Zmin)/(Zmax - Zmin)
print(Z) print(Z)
#. Create a custom dtype that describes a color as four unisgned bytes (RGBA) (★☆☆)
.. code-block:: python
color = np.dtype([("r", np.ubyte, 1),
("g", np.ubyte, 1),
("b", np.ubyte, 1),
("a", np.ubyte, 1)])
#. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆) #. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆)
@@ -210,6 +218,59 @@ Thanks to Michiaki Ariga, there is now a
Z = np.arange(11) Z = np.arange(11)
Z[(3 < Z) & (Z <= 8)] *= -1 Z[(3 < Z) & (Z <= 8)] *= -1
#. What is the output of the following script? (★☆☆)
.. code-block:: python
# Author: Jake VanderPlas
print(sum(range(5),-1))
from numpy import *
print(sum(range(5),-1))
#. Consider an integer vector Z, which of these expressions are legal? (★☆☆)
.. code-block:: python
Z**Z
2 << Z >> 2
Z <- Z
1j*Z
Z/1/1
Z<Z>Z
#. What are the result of the following expressions?
.. code-block:: python
np.array(0) // np.array(0)
np.array(0) // np.array(0.)
np.array(0) / np.array(0)
np.array(0) / np.array(0.)
#. How to round away from zero a float array ? (★☆☆)
.. code-block:: python
# Author: Charles R Harris
Z = np.random.uniform(-10,+10,10)
print (np.trunc(Z + np.copysign(0.5, Z)))
#. Extract the integer part of a random array using 5 different methods (★★☆)
.. code-block:: python
Z = np.random.uniform(0,10,10)
print (Z - Z%1)
print (np.floor(Z))
print (np.ceil(Z)-1)
print (Z.astype(int))
print (np.trunc(Z))
#. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆) #. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆)
@@ -394,15 +455,16 @@ Thanks to Michiaki Ariga, there is now a
Z = Z.astype(np.float32, copy=False) Z = Z.astype(np.float32, copy=False)
#. Consider the following file:: #. How to read the following file? (★★☆)
.. code-block:: python
# File content:
# -------------
1,2,3,4,5 1,2,3,4,5
6,,,7,8 6,,,7,8
,,9,10,11 ,,9,10,11
# -------------
How to read it ? (★★☆)
.. code-block:: python
Z = np.genfromtxt("missing.dat", delimiter=",") Z = np.genfromtxt("missing.dat", delimiter=",")
@@ -484,6 +546,21 @@ Thanks to Michiaki Ariga, there is now a
print(m) print(m)
#. Create an array class that has a `name` attribute (★★☆)
.. code-block:: python
class NamedArray(np.ndarray):
def __new__(cls, array, name="no name"):
obj = np.asarray(array).view(cls)
obj.name = name
return obj
def __array_finalize__(self, obj):
if obj is None: return
self.info = getattr(obj, 'name', "no name")
Z = NamedArray(np.arange(10), "range_10")
print (Z.name)
@@ -903,7 +980,7 @@ Thanks to Michiaki Ariga, there is now a
names='col1, col2, col3', names='col1, col2, col3',
formats = 'S8, f8, i8') formats = 'S8, f8, i8')
#. Comsider a large vector Z, compute Z to the power of 3 using 3 different #. Consider a large vector Z, compute Z to the power of 3 using 3 different
methods (★★★) methods (★★★)
.. code-block:: python .. code-block:: python
@@ -951,7 +1028,6 @@ Thanks to Michiaki Ariga, there is now a
print(U) print(U)
#. Convert a vector of ints into a matrix binary representation (★★★) #. Convert a vector of ints into a matrix binary representation (★★★)
.. code-block:: python .. code-block:: python