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python-cheatsheet
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Duck types, NumPy, Cython

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Jure Šorn 3 months ago
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  1. 10
      README.md
  2. 14
      index.html

10
README.md
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@ -1164,7 +1164,7 @@ class MySortable:
### Iterator
* **Any object that has methods next() and iter() is an iterator.**
* **Next() should return next item or raise StopIteration exception.**
* **Iter() should return 'self'.**
* **Iter() should return 'self', i.e. unmodified object on which it was called.**
```python
class Counter:
def __init__(self):
@ -2718,14 +2718,14 @@ import numpy as np
### Broadcasting
**A set of rules by which NumPy functions operate on arrays of different shapes.**
```python
left = np.array([ 0.1, 0.6, 0.8 ]) # `left.shape == (3,)`
right = np.array([[0.1],[0.6],[0.8]]) # `right.shape == (3, 1)`
left = np.array([0.1, 0.6, 0.8]) # `left.shape == (3,)`
right = np.array([[0.1], [0.6], [0.8]]) # `right.shape == (3, 1)`
```
#### 1. If array shapes differ in length, left-pad the shorter shape with ones:
```python
left = np.array([[0.1, 0.6, 0.8]]) # `left.shape == (1, 3)`
right = np.array([[0.1],[0.6],[0.8]]) # `right.shape == (3, 1)`
right = np.array([[0.1], [0.6], [0.8]]) # `right.shape == (3, 1)`
```
#### 2. If any dimensions differ in size, expand the ones that have size 1 by duplicating their elements:
@ -3525,7 +3525,7 @@ Appendix
```python
# $ pip3 install cython
import pyximport; pyximport.install() # Module that runs imported Cython scripts.
import <cython_script> # Script's filename needs a '.pyx' extension.
import <cython_script> # Script must be saved with '.pyx' extension.
<cython_script>.main() # Main() isn't automatically executed.
```

14
index.html
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@ -55,7 +55,7 @@
<body>
<header>
<aside>December 25, 2024</aside>
<aside>December 26, 2024</aside>
<a href="https://gto76.github.io" rel="author">Jure Šorn</a>
</header>
@ -978,7 +978,7 @@ Point = make_dataclass(<span class="hljs-string">'Point'</span>, [(<span class="
<div><h3 id="iterator-1">Iterator</h3><ul>
<li><strong>Any object that has methods next() and iter() is an iterator.</strong></li>
<li><strong>Next() should return next item or raise StopIteration exception.</strong></li>
<li><strong>Iter() should return 'self'.</strong></li>
<li><strong>Iter() should return 'self', i.e. unmodified object on which it was called.</strong></li>
</ul><pre><code class="python language-python hljs"><span class="hljs-class"><span class="hljs-keyword">class</span> <span class="hljs-title">Counter</span>:</span>
<span class="hljs-function"><span class="hljs-keyword">def</span> <span class="hljs-title">__init__</span><span class="hljs-params">(self)</span>:</span>
self.i = <span class="hljs-number">0</span>
@ -2216,13 +2216,13 @@ $ snakeviz test.prof <span class="hlj
<li><strong><code class="python hljs"><span class="hljs-string">'ix_([1, 2], [3, 4])'</span></code> returns <code class="python hljs"><span class="hljs-string">'[[1], [2]]'</span></code> and <code class="python hljs"><span class="hljs-string">'[[3, 4]]'</span></code>. Due to broadcasting rules, this is the same as using <code class="python hljs"><span class="hljs-string">'[[1, 1], [2, 2]]'</span></code> and <code class="python hljs"><span class="hljs-string">'[[3, 4], [3, 4]]'</span></code>.</strong></li>
<li><strong>Any value that is broadcastable to the indexed shape can be assigned to the selection.</strong></li>
</ul>
<div><h3 id="broadcasting">Broadcasting</h3><p><strong>A set of rules by which NumPy functions operate on arrays of different shapes.</strong></p><pre><code class="python language-python hljs">left = np.array([ <span class="hljs-number">0.1</span>, <span class="hljs-number">0.6</span>, <span class="hljs-number">0.8</span> ]) <span class="hljs-comment"># `left.shape == (3,)`</span>
right = np.array([[<span class="hljs-number">0.1</span>],[<span class="hljs-number">0.6</span>],[<span class="hljs-number">0.8</span>]]) <span class="hljs-comment"># `right.shape == (3, 1)`</span>
<div><h3 id="broadcasting">Broadcasting</h3><p><strong>A set of rules by which NumPy functions operate on arrays of different shapes.</strong></p><pre><code class="python language-python hljs">left = np.array([<span class="hljs-number">0.1</span>, <span class="hljs-number">0.6</span>, <span class="hljs-number">0.8</span>]) <span class="hljs-comment"># `left.shape == (3,)`</span>
right = np.array([[<span class="hljs-number">0.1</span>], [<span class="hljs-number">0.6</span>], [<span class="hljs-number">0.8</span>]]) <span class="hljs-comment"># `right.shape == (3, 1)`</span>
</code></pre></div>
<div><h4 id="1ifarrayshapesdifferinlengthleftpadtheshortershapewithones">1. If array shapes differ in length, left-pad the shorter shape with ones:</h4><pre><code class="python language-python hljs">left = np.array([[<span class="hljs-number">0.1</span>, <span class="hljs-number">0.6</span>, <span class="hljs-number">0.8</span>]]) <span class="hljs-comment"># `left.shape == (1, 3)`</span>
right = np.array([[<span class="hljs-number">0.1</span>],[<span class="hljs-number">0.6</span>],[<span class="hljs-number">0.8</span>]]) <span class="hljs-comment"># `right.shape == (3, 1)`</span>
right = np.array([[<span class="hljs-number">0.1</span>], [<span class="hljs-number">0.6</span>], [<span class="hljs-number">0.8</span>]]) <span class="hljs-comment"># `right.shape == (3, 1)`</span>
</code></pre></div>
<div><h4 id="2ifanydimensionsdifferinsizeexpandtheonesthathavesize1byduplicatingtheirelements">2. If any dimensions differ in size, expand the ones that have size 1 by duplicating their elements:</h4><pre><code class="python language-python hljs">left = np.array([[<span class="hljs-number">0.1</span>, <span class="hljs-number">0.6</span>, <span class="hljs-number">0.8</span>], <span class="hljs-comment"># `left.shape == (3, 3)`</span>
@ -2868,7 +2868,7 @@ px.line(df, x=<span class="hljs-string">'Date'</span>, y=<span class="hljs-strin
<div><h2 id="appendix"><a href="#appendix" name="appendix">#</a>Appendix</h2><div><h3 id="cython">Cython</h3><p><strong>Library that compiles Python-like code into C.</strong></p><pre><code class="python language-python hljs"><span class="hljs-comment"># $ pip3 install cython</span>
<span class="hljs-keyword">import</span> pyximport; pyximport.install() <span class="hljs-comment"># Module that runs imported Cython scripts.</span>
<span class="hljs-keyword">import</span> &lt;cython_script&gt; <span class="hljs-comment"># Script's filename needs a '.pyx' extension.</span>
<span class="hljs-keyword">import</span> &lt;cython_script&gt; <span class="hljs-comment"># Script must be saved with '.pyx' extension.</span>
&lt;cython_script&gt;.main() <span class="hljs-comment"># Main() isn't automatically executed.</span>
</code></pre></div></div>
@ -2934,7 +2934,7 @@ $ deactivate <span class="hljs-comment"># Deactivates the active
<footer>
<aside>December 25, 2024</aside>
<aside>December 26, 2024</aside>
<a href="https://gto76.github.io" rel="author">Jure Šorn</a>
</footer>

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