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                        <h1 id="python"><a class="header" href="#python">python</a></h1>
<h2 id="decorator-run"><a class="header" href="#decorator-run">Decorator [<a href="https://www.online-python.com/IDdiE0gpYU">run</a>]</a></h2>
<p>Some decorator examples with type annotation.</p>
<pre><code class="language-python">from typing import Callable

def log(f: Callable[[int], None]) -&gt; Callable[[int], None]:
    def inner(x: int):
        print(f&quot;log::inner f={f.__name__} x={x}&quot;)
        f(x)
    return inner

@log
def some_fn(x: int):
    print(f&quot;some_fn x={x}&quot;)


def log_tag(tag: str) -&gt; Callable[[Callable[[int], None]], Callable[[int], None]]:
    def decorator(f: Callable[[int], None]) -&gt; Callable[[int], None]:
        def inner(x: int):
            print(f&quot;log_tag::inner f={f.__name__} tag={tag} x={x}&quot;)
            f(x)
        return inner
    return decorator

@log_tag(&quot;some_tag&quot;)
def some_fn2(x: int):
    print(f&quot;some_fn2 x={x}&quot;)
</code></pre>
<h2 id="walrus-operator-run"><a class="header" href="#walrus-operator-run">Walrus operator [<a href="https://www.online-python.com/9T12PvmKVy">run</a>]</a></h2>
<p>Walrus operator <code>:=</code> added since <strong>python 3.8</strong>.</p>
<pre><code class="language-python">from typing import Optional

# Example 1: if let statements

def foo(ret: Optional[int]) -&gt; Optional[int]:
    return ret

if r := foo(None):
    print(f&quot;foo(None) -&gt; {r}&quot;)

if r := foo(1337):
    print(f&quot;foo(1337) -&gt; {r}&quot;)

# Example 2: while let statements

toks = iter(['a', 'b', 'c'])
while tok := next(toks, None):
    print(f&quot;{tok}&quot;)

# Example 3: list comprehension

print([tok for t in [&quot;  a&quot;, &quot;  &quot;, &quot; b &quot;] if (tok := t.strip())])
</code></pre>
<h2 id="unittest-run"><a class="header" href="#unittest-run"><a href="https://docs.python.org/3/library/unittest.html">Unittest</a> [<a href="https://www.online-python.com/2fit4UcbzI">run</a>]</a></h2>
<p>Run unittests directly from the command line as <br />
<code>python3 -m unittest -v test</code></p>
<p>Optionally pass <code>-k &lt;patter&gt;</code> to only run subset of tests.</p>
<pre><code class="language-python"># file: test.py

import unittest

class MyTest(unittest.TestCase):
    def setUp(self):
        pass
    def tearDown(self):
        pass
    # Tests need to start with the prefix 'test'.
    def test_foo(self):
        self.assertEqual(1 + 2, 3)
    def test_bar(self):
        with self.assertRaises(IndexError):
            list()[0]
</code></pre>
<h2 id="doctest-run"><a class="header" href="#doctest-run"><a href="https://docs.python.org/3/library/doctest.html">Doctest</a> [<a href="https://www.online-python.com/LZst51UNIH">run</a>]</a></h2>
<p>Run doctests directly from the command line as <br />
<code>python -m doctest -v test.py</code></p>
<pre><code class="language-python"># file: test.py

def sum(a: int, b: int) -&gt; int:
    &quot;&quot;&quot;Sum a and b.

    &gt;&gt;&gt; sum(1, 2)
    3

    &gt;&gt;&gt; sum(10, 20)
    30
    &quot;&quot;&quot;
    return a + b
</code></pre>
<h2 id="timeit"><a class="header" href="#timeit"><a href="https://docs.python.org/3/library/timeit.html">timeit</a></a></h2>
<p>Micro benchmarking.</p>
<pre><code class="language-bash">python -m timeit '[x.strip() for x in [&quot;a &quot;, &quot; b&quot;]]'
</code></pre>

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