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python-cheatsheet
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List, Datetime, Operator

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Jure Šorn 5 months ago
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  1. 18
      README.md
  2. 21
      index.html
  3. 2
      pdf/remove_links.py

18
README.md
View File

@ -50,15 +50,17 @@ List
```
```python
sum_of_elements = sum(<collection>)
<el> = max(<collection>) # Returns largest element. Also max(<el_1>, ...).
<num> = sum(<collection>) # Returns sum of elements. Also math.prod(<coll>).
```
```python
elementwise_sum = [sum(pair) for pair in zip(list_a, list_b)]
sorted_by_second = sorted(<collection>, key=lambda el: el[1])
sorted_by_both = sorted(<collection>, key=lambda el: (el[1], el[0]))
flatter_list = list(itertools.chain.from_iterable(<list>))
product_of_elems = functools.reduce(lambda out, el: out * el, <collection>)
list_of_chars = list(<str>)
```
* **For details about sorted(), min() and max() see [sortable](#sortable).**
* **For details about sort(), sorted(), max() and min() see [sortable](#sortable).**
* **Module [operator](#operator) provides functions itemgetter() and mul() that offer the same functionality as [lambda](#lambda) expressions above.**
```python
@ -388,7 +390,6 @@ import re
'\w' == '[a-zA-Z0-9_]' # Also [ª²³…]. Matches an alphanumeric or _.
'\s' == '[ \t\n\r\f\v]' # Also [\x1c-\x1f…]. Matches a whitespace.
```
* **By default, decimal characters, alphanumerics and whitespaces from all alphabets are matched unless `'flags=re.ASCII'` argument is used.**
* **It restricts special sequence matches to `'[\x00-\x7f]'` (the first 128 characters) and also prevents `'\s'` from accepting `'[\x1c-\x1f]'` (file, table, row, and field separators).**
* **Use a capital letter for negation (all non-ASCII characters will be matched when used in combination with ASCII flag).**
@ -605,7 +606,7 @@ import zoneinfo, dateutil.tz
<DT> = datetime(year, month, day, hour=0) # Also: `minute=0, second=0, microsecond=0, …`.
<TD> = timedelta(weeks=0, days=0, hours=0) # Also: `minutes=0, seconds=0, microseconds=0`.
```
* **Aware `<a>` time and datetime objects have defined timezone, while naive `<n>` don't. If object is naive, it is presumed to be in the system's timezone!**
* **Aware times and datetimes have defined timezone, while naive don't. If object is naive, it is presumed to be in the system's timezone!**
* **`'fold=1'` means the second pass in case of time jumping back for one hour.**
* **Timedelta normalizes arguments to ±days, seconds (< 86 400) and microseconds (< 1M). Its str() method returns `'[±D, ]H:MM:SS[.…]'` and total_seconds() a float of all seconds.**
* **Use `'<D/DT>.weekday()'` to get the day of the week as an int, with Monday being 0.**
@ -2185,9 +2186,8 @@ import operator as op
```python
elementwise_sum = map(op.add, list_a, list_b)
sorted_by_second = sorted(<coll.>, key=op.itemgetter(1))
sorted_by_both = sorted(<coll.>, key=op.itemgetter(1, 0))
product_of_elems = functools.reduce(op.mul, <collection>)
sorted_by_second = sorted(<coll>, key=op.itemgetter(1))
sorted_by_both = sorted(<coll>, key=op.itemgetter(1, 0))
first_element = op.methodcaller('pop', 0)(<list>)
```
* **Most operators call the object's special method that is named after them (second object is passed as an argument), while logical operators call their own code that relies on bool().**

21
index.html
View File

@ -55,7 +55,7 @@
<body>
<header>
<aside>November 13, 2024</aside>
<aside>November 14, 2024</aside>
<a href="https://gto76.github.io" rel="author">Jure Šorn</a>
</header>
@ -114,16 +114,16 @@
&lt;list&gt; = sorted(&lt;collection&gt;) <span class="hljs-comment"># Returns new list with sorted elements.</span>
&lt;iter&gt; = reversed(&lt;list&gt;) <span class="hljs-comment"># Returns reversed iterator of elements.</span>
</code></pre>
<pre><code class="python language-python hljs">sum_of_elements = sum(&lt;collection&gt;)
elementwise_sum = [sum(pair) <span class="hljs-keyword">for</span> pair <span class="hljs-keyword">in</span> zip(list_a, list_b)]
<pre><code class="python language-python hljs">&lt;el&gt; = max(&lt;collection&gt;) <span class="hljs-comment"># Returns largest element. Also max(&lt;el_1&gt;, ...).</span>
&lt;num&gt; = sum(&lt;collection&gt;) <span class="hljs-comment"># Returns sum of elements. Also math.prod(&lt;coll&gt;).</span>
</code></pre>
<pre><code class="python language-python hljs">elementwise_sum = [sum(pair) <span class="hljs-keyword">for</span> pair <span class="hljs-keyword">in</span> zip(list_a, list_b)]
sorted_by_second = sorted(&lt;collection&gt;, key=<span class="hljs-keyword">lambda</span> el: el[<span class="hljs-number">1</span>])
sorted_by_both = sorted(&lt;collection&gt;, key=<span class="hljs-keyword">lambda</span> el: (el[<span class="hljs-number">1</span>], el[<span class="hljs-number">0</span>]))
flatter_list = list(itertools.chain.from_iterable(&lt;list&gt;))
product_of_elems = functools.reduce(<span class="hljs-keyword">lambda</span> out, el: out * el, &lt;collection&gt;)
list_of_chars = list(&lt;str&gt;)
</code></pre>
<ul>
<li><strong>For details about sorted(), min() and max() see <a href="#sortable">sortable</a>.</strong></li>
<li><strong>For details about sort(), sorted(), max() and min() see <a href="#sortable">sortable</a>.</strong></li>
<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; = len(&lt;list&gt;) <span class="hljs-comment"># Returns number of items. Also works on other collections.</span>
@ -527,7 +527,7 @@ Point(x=<span class="hljs-number">1</span>, y=<span class="hljs-number">2</span>
&lt;TD&gt; = timedelta(weeks=<span class="hljs-number">0</span>, days=<span class="hljs-number">0</span>, hours=<span class="hljs-number">0</span>) <span class="hljs-comment"># Also: `minutes=0, seconds=0, microseconds=0`.</span>
</code></pre>
<ul>
<li><strong>Aware <code class="apache hljs"><span class="hljs-section">&lt;a&gt;</span></code> time and datetime objects have defined timezone, while naive <code class="apache hljs"><span class="hljs-section">&lt;n&gt;</span></code> don't. If object is naive, it is presumed to be in the system's timezone!</strong></li>
<li><strong>Aware times and datetimes have defined timezone, while naive don't. If object is naive, it is presumed to be in the system's timezone!</strong></li>
<li><strong><code class="python hljs"><span class="hljs-string">'fold=1'</span></code> means the second pass in case of time jumping back for one hour.</strong></li>
<li><strong>Timedelta normalizes arguments to ±days, seconds (&lt; 86 400) and microseconds (&lt; 1M). Its str() method returns <code class="python hljs"><span class="hljs-string">'[±D, ]H:MM:SS[.…]'</span></code> and total_seconds() a float of all seconds.</strong></li>
<li><strong>Use <code class="python hljs"><span class="hljs-string">'&lt;D/DT&gt;.weekday()'</span></code> to get the day of the week as an int, with Monday being 0.</strong></li>
@ -1789,9 +1789,8 @@ CompletedProcess(args=[<span class="hljs-string">'bc'</span>, <span class="hljs-
&lt;func&gt; = op.itemgetter/attrgetter/methodcaller(&lt;obj&gt; [, ...]) <span class="hljs-comment"># [index/key], .name, .name([…])</span>
</code></pre>
<pre><code class="python language-python hljs">elementwise_sum = map(op.add, list_a, list_b)
sorted_by_second = sorted(&lt;coll.&gt;, key=op.itemgetter(<span class="hljs-number">1</span>))
sorted_by_both = sorted(&lt;coll.&gt;, key=op.itemgetter(<span class="hljs-number">1</span>, <span class="hljs-number">0</span>))
product_of_elems = functools.reduce(op.mul, &lt;collection&gt;)
sorted_by_second = sorted(&lt;coll&gt;, key=op.itemgetter(<span class="hljs-number">1</span>))
sorted_by_both = sorted(&lt;coll&gt;, key=op.itemgetter(<span class="hljs-number">1</span>, <span class="hljs-number">0</span>))
first_element = op.methodcaller(<span class="hljs-string">'pop'</span>, <span class="hljs-number">0</span>)(&lt;list&gt;)
</code></pre>
<ul>
@ -2924,7 +2923,7 @@ $ deactivate <span class="hljs-comment"># Deactivates the active
<footer>
<aside>November 13, 2024</aside>
<aside>November 14, 2024</aside>
<a href="https://gto76.github.io" rel="author">Jure Šorn</a>
</footer>

2
pdf/remove_links.py
View File

@ -7,7 +7,7 @@ from pathlib import Path
MATCHES = {
'<strong>For details about sorted(), min() and max() see <a href="#sortable">sortable</a>.</strong>': '<strong>For details about sorted(), min() and max() see sortable (p. 16).</strong>',
'<strong>For details about sort(), sorted(), max() and min() see <a href="#sortable">sortable</a>.</strong>': '<strong>For details about sort(), sorted(), max() and min() see sortable (p. 16).</strong>',
'<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>': '<strong>Module \'operator\' (p. 31) provides functions itemgetter() and mul() that offer the same functionality as lambda expressions (p. 11) above.</strong>',
'<strong>Adding <code class="python hljs"><span class="hljs-string">\'!r\'</span></code> to the expression converts object to string by calling its <a href="#class">repr()</a> method.</strong>': '<strong>Adding <code class="python hljs"><span class="hljs-string">\'!r\'</span></code> to the expression converts object to string by calling its repr() method.</strong>',
'<strong>It can be any <a href="#callable">callable</a>, but is usually implemented as a function that returns a <a href="#closure">closure</a>.</strong>': '<strong>It can be any callable, but is usually implemented as a function that returns a closure.</strong>',

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