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python-cheatsheet
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List, String, Numbers, Curses, Scraping

pull/86/head
Jure Šorn 4 years ago
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2 changed files with 42 additions and 40 deletions
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  1. 41
      README.md
  2. 41
      index.html

41
README.md
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@ -57,10 +57,10 @@ list_of_chars = list(<str>)
```python
<int> = <list>.count(<el>) # Returns number of occurrences. Also works on strings.
index = <list>.index(<el>) # Returns index of first occurrence or raises ValueError.
<list>.insert(index, <el>) # Inserts item at index and moves the rest to the right.
<el> = <list>.pop([index]) # Removes and returns item at index or from the end.
<list>.remove(<el>) # Removes first occurrence of item or raises ValueError.
<int> = <list>.index(<el>) # Returns index of the first occurrence or raises ValueError.
<list>.insert(<int>, <el>) # Inserts item at index and moves the rest to the right.
<el> = <list>.pop([<int>]) # Removes and returns item at index or from the end.
<list>.remove(<el>) # Removes first occurrence of the item or raises ValueError.
<list>.clear() # Removes all items. Also works on dictionary and set.
```
@ -309,14 +309,14 @@ String
<list> = <str>.split() # Splits on one or more whitespace characters.
<list> = <str>.split(sep=None, maxsplit=-1) # Splits on 'sep' str at most 'maxsplit' times.
<list> = <str>.splitlines(keepends=False) # Splits on \n,\r,\r\n. Keeps them if 'keepends'.
<str> = <str>.join(<coll_of_strings>) # Joins elements using string as separator.
<str> = <str>.join(<coll_of_strings>) # Joins elements using string as a separator.
```
```python
<bool> = <sub_str> in <str> # Checks if string contains a substring.
<bool> = <str>.startswith(<sub_str>) # Pass tuple of strings for multiple options.
<bool> = <str>.endswith(<sub_str>) # Pass tuple of strings for multiple options.
<int> = <str>.find(<sub_str>) # Returns start index of first match or -1.
<int> = <str>.find(<sub_str>) # Returns start index of the first match or -1.
<int> = <str>.index(<sub_str>) # Same but raises ValueError if missing.
```
@ -512,10 +512,10 @@ from statistics import mean, median, variance, stdev, pvariance, pstdev
### Random
```python
from random import random, randint, choice, shuffle, gauss, seed
<float> = random()
<int> = randint(from_inclusive, to_inclusive)
<el> = choice(<list>)
shuffle(<list>)
```
### Bin, Hex
@ -2381,8 +2381,8 @@ def main(screen):
while ch != ascii.ESC:
height, _ = screen.getmaxyx()
screen.clear()
for y, path_ in enumerate(paths[first : first+height]):
screen.addstr(y, 0, path_, A_REVERSE * (selected == first + y))
for y, a_path in enumerate(paths[first : first+height]):
screen.addstr(y, 0, a_path, A_REVERSE * (selected == first + y))
ch = screen.getch()
selected += (ch == KEY_DOWN) - (ch == KEY_UP)
selected = max(0, min(len(paths)-1, selected))
@ -2448,18 +2448,19 @@ Scraping
```python
# $ pip3 install requests beautifulsoup4
import requests, bs4, sys
URL = 'https://en.wikipedia.org/wiki/Python_(programming_language)'
WIKI_URL = 'https://en.wikipedia.org/wiki/Python_(programming_language)'
try:
html = requests.get(URL).text
doc = bs4.BeautifulSoup(html, 'html.parser')
table = doc.find('table', class_='infobox vevent')
link = table.find('th', text='Website').next_sibling.a['href']
ver = table.find('th', text='Stable release').next_sibling.strings.__next__()
url_i = table.find('img')['src']
image = requests.get(f'https:{url_i}').content
html = requests.get(WIKI_URL).text
document = bs4.BeautifulSoup(html, 'html.parser')
table = document.find('table', class_='infobox vevent')
python_url = table.find('th', text='Website').next_sibling.a['href']
version = table.find('th', text='Stable release').next_sibling.strings.__next__()
logo_url = table.find('img')['src']
logo = requests.get(f'https:{logo_url}').content
with open('test.png', 'wb') as file:
file.write(image)
print(link, ver)
file.write(logo)
print(python_url, version)
except requests.exceptions.ConnectionError:
print("You've got problems with connection.", file=sys.stderr)
```
@ -2614,7 +2615,7 @@ indexes = <array>.argmin(axis)
```
* **Shape is a tuple of dimension sizes.**
* **Axis is the index of a dimension that gets collapsed. The leftmost dimension has index 0.**
* **Axis is an index of the dimension that gets collapsed. Leftmost dimension has index 0.**
### Indexing
```bash

41
index.html
View File

@ -276,10 +276,10 @@ list_of_chars = list(&lt;str&gt;)
<li><strong>Module <a href="#operator">operator</a> provides functions itemgetter() and mul() that offer the same functionality as <a href="#lambda">lambda</a> expressions above.</strong></li>
</ul>
<pre><code class="python language-python hljs">&lt;int&gt; = &lt;list&gt;.count(&lt;el&gt;) <span class="hljs-comment"># Returns number of occurrences. Also works on strings.</span>
index = &lt;list&gt;.index(&lt;el&gt;) <span class="hljs-comment"># Returns index of first occurrence or raises ValueError.</span>
&lt;list&gt;.insert(index, &lt;el&gt;) <span class="hljs-comment"># Inserts item at index and moves the rest to the right.</span>
&lt;el&gt; = &lt;list&gt;.pop([index]) <span class="hljs-comment"># Removes and returns item at index or from the end.</span>
&lt;list&gt;.remove(&lt;el&gt;) <span class="hljs-comment"># Removes first occurrence of item or raises ValueError.</span>
&lt;int&gt; = &lt;list&gt;.index(&lt;el&gt;) <span class="hljs-comment"># Returns index of the first occurrence or raises ValueError.</span>
&lt;list&gt;.insert(&lt;int&gt;, &lt;el&gt;) <span class="hljs-comment"># Inserts item at index and moves the rest to the right.</span>
&lt;el&gt; = &lt;list&gt;.pop([&lt;int&gt;]) <span class="hljs-comment"># Removes and returns item at index or from the end.</span>
&lt;list&gt;.remove(&lt;el&gt;) <span class="hljs-comment"># Removes first occurrence of the item or raises ValueError.</span>
&lt;list&gt;.clear() <span class="hljs-comment"># Removes all items. Also works on dictionary and set.</span>
</code></pre>
<div><h2 id="dictionary"><a href="#dictionary" name="dictionary">#</a>Dictionary</h2><pre><code class="python language-python hljs">&lt;view&gt; = &lt;dict&gt;.keys() <span class="hljs-comment"># Coll. of keys that reflects changes.</span>
@ -450,12 +450,12 @@ to_exclusive = &lt;range&gt;.stop
<pre><code class="python language-python hljs">&lt;list&gt; = &lt;str&gt;.split() <span class="hljs-comment"># Splits on one or more whitespace characters.</span>
&lt;list&gt; = &lt;str&gt;.split(sep=<span class="hljs-keyword">None</span>, maxsplit=<span class="hljs-number">-1</span>) <span class="hljs-comment"># Splits on 'sep' str at most 'maxsplit' times.</span>
&lt;list&gt; = &lt;str&gt;.splitlines(keepends=<span class="hljs-keyword">False</span>) <span class="hljs-comment"># Splits on \n,\r,\r\n. Keeps them if 'keepends'.</span>
&lt;str&gt; = &lt;str&gt;.join(&lt;coll_of_strings&gt;) <span class="hljs-comment"># Joins elements using string as separator.</span>
&lt;str&gt; = &lt;str&gt;.join(&lt;coll_of_strings&gt;) <span class="hljs-comment"># Joins elements using string as a separator.</span>
</code></pre>
<pre><code class="python language-python hljs">&lt;bool&gt; = &lt;sub_str&gt; <span class="hljs-keyword">in</span> &lt;str&gt; <span class="hljs-comment"># Checks if string contains a substring.</span>
&lt;bool&gt; = &lt;str&gt;.startswith(&lt;sub_str&gt;) <span class="hljs-comment"># Pass tuple of strings for multiple options.</span>
&lt;bool&gt; = &lt;str&gt;.endswith(&lt;sub_str&gt;) <span class="hljs-comment"># Pass tuple of strings for multiple options.</span>
&lt;int&gt; = &lt;str&gt;.find(&lt;sub_str&gt;) <span class="hljs-comment"># Returns start index of first match or -1.</span>
&lt;int&gt; = &lt;str&gt;.find(&lt;sub_str&gt;) <span class="hljs-comment"># Returns start index of the first match or -1.</span>
&lt;int&gt; = &lt;str&gt;.index(&lt;sub_str&gt;) <span class="hljs-comment"># Same but raises ValueError if missing.</span>
</code></pre>
<pre><code class="python language-python hljs">&lt;str&gt; = &lt;str&gt;.replace(old, new [, count]) <span class="hljs-comment"># Replaces 'old' with 'new' at most 'count' times.</span>
@ -614,10 +614,10 @@ to_exclusive = &lt;range&gt;.stop
</code></pre></div>
<div><h3 id="random">Random</h3><pre><code class="python language-python hljs"><span class="hljs-keyword">from</span> random <span class="hljs-keyword">import</span> random, randint, choice, shuffle, gauss, seed
&lt;float&gt; = random()
&lt;int&gt; = randint(from_inclusive, to_inclusive)
&lt;el&gt; = choice(&lt;list&gt;)
shuffle(&lt;list&gt;)
</code></pre></div>
<div><h3 id="binhex">Bin, Hex</h3><pre><code class="python language-python hljs">&lt;int&gt; = ±<span class="hljs-number">0</span>b&lt;bin&gt; <span class="hljs-comment"># Or: ±0x&lt;hex&gt;</span>
@ -2087,8 +2087,8 @@ plt.clf() <span class="hljs-comment"># Clea
<span class="hljs-keyword">while</span> ch != ascii.ESC:
height, _ = screen.getmaxyx()
screen.clear()
<span class="hljs-keyword">for</span> y, path_ <span class="hljs-keyword">in</span> enumerate(paths[first : first+height]):
screen.addstr(y, <span class="hljs-number">0</span>, path_, A_REVERSE * (selected == first + y))
<span class="hljs-keyword">for</span> y, a_path <span class="hljs-keyword">in</span> enumerate(paths[first : first+height]):
screen.addstr(y, <span class="hljs-number">0</span>, a_path, A_REVERSE * (selected == first + y))
ch = screen.getch()
selected += (ch == KEY_DOWN) - (ch == KEY_UP)
selected = max(<span class="hljs-number">0</span>, min(len(paths)<span class="hljs-number">-1</span>, selected))
@ -2143,18 +2143,19 @@ logger.&lt;level&gt;(<span class="hljs-string">'A logging message.'</span>)
</ul>
<div><h2 id="scraping"><a href="#scraping" name="scraping">#</a>Scraping</h2><div><h4 id="scrapespythonsurlversionnumberandlogofromitswikipediapage">Scrapes Python's URL, version number and logo from its Wikipedia page:</h4><pre><code class="python language-python hljs"><span class="hljs-comment"># $ pip3 install requests beautifulsoup4</span>
<span class="hljs-keyword">import</span> requests, bs4, sys
URL = <span class="hljs-string">'https://en.wikipedia.org/wiki/Python_(programming_language)'</span>
WIKI_URL = <span class="hljs-string">'https://en.wikipedia.org/wiki/Python_(programming_language)'</span>
<span class="hljs-keyword">try</span>:
html = requests.get(URL).text
doc = bs4.BeautifulSoup(html, <span class="hljs-string">'html.parser'</span>)
table = doc.find(<span class="hljs-string">'table'</span>, class_=<span class="hljs-string">'infobox vevent'</span>)
link = table.find(<span class="hljs-string">'th'</span>, text=<span class="hljs-string">'Website'</span>).next_sibling.a[<span class="hljs-string">'href'</span>]
ver = table.find(<span class="hljs-string">'th'</span>, text=<span class="hljs-string">'Stable release'</span>).next_sibling.strings.__next__()
url_i = table.find(<span class="hljs-string">'img'</span>)[<span class="hljs-string">'src'</span>]
image = requests.get(<span class="hljs-string">f'https:<span class="hljs-subst">{url_i}</span>'</span>).content
html = requests.get(WIKI_URL).text
document = bs4.BeautifulSoup(html, <span class="hljs-string">'html.parser'</span>)
table = document.find(<span class="hljs-string">'table'</span>, class_=<span class="hljs-string">'infobox vevent'</span>)
python_url = table.find(<span class="hljs-string">'th'</span>, text=<span class="hljs-string">'Website'</span>).next_sibling.a[<span class="hljs-string">'href'</span>]
version = table.find(<span class="hljs-string">'th'</span>, text=<span class="hljs-string">'Stable release'</span>).next_sibling.strings.__next__()
logo_url = table.find(<span class="hljs-string">'img'</span>)[<span class="hljs-string">'src'</span>]
logo = requests.get(<span class="hljs-string">f'https:<span class="hljs-subst">{logo_url}</span>'</span>).content
<span class="hljs-keyword">with</span> open(<span class="hljs-string">'test.png'</span>, <span class="hljs-string">'wb'</span>) <span class="hljs-keyword">as</span> file:
file.write(image)
print(link, ver)
file.write(logo)
print(python_url, version)
<span class="hljs-keyword">except</span> requests.exceptions.ConnectionError:
print(<span class="hljs-string">"You've got problems with connection."</span>, file=sys.stderr)
</code></pre></div></div>
@ -2270,7 +2271,7 @@ indexes = &lt;array&gt;.argmin(axis)
</code></pre>
<ul>
<li><strong>Shape is a tuple of dimension sizes.</strong></li>
<li><strong>Axis is the index of a dimension that gets collapsed. The leftmost dimension has index 0.</strong></li>
<li><strong>Axis is an index of the dimension that gets collapsed. Leftmost dimension has index 0.</strong></li>
</ul>
<div><h3 id="indexing">Indexing</h3><pre><code class="python language-python hljs">&lt;el&gt; = &lt;2d_array&gt;[<span class="hljs-number">0</span>, <span class="hljs-number">0</span>] <span class="hljs-comment"># First element.</span>
&lt;1d_view&gt; = &lt;2d_array&gt;[<span class="hljs-number">0</span>] <span class="hljs-comment"># First row.</span>

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