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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]) -> Callable[[int], None]:
def inner(x: int):
print(f"log::inner f={f.__name__} x={x}")
f(x)
return inner
@log
def some_fn(x: int):
print(f"some_fn x={x}")
def log_tag(tag: str) -> Callable[[Callable[[int], None]], Callable[[int], None]]:
def decorator(f: Callable[[int], None]) -> Callable[[int], None]:
def inner(x: int):
print(f"log_tag::inner f={f.__name__} tag={tag} x={x}")
f(x)
return inner
return decorator
@log_tag("some_tag")
def some_fn2(x: int):
print(f"some_fn2 x={x}")
</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]) -> Optional[int]:
return ret
if r := foo(None):
print(f"foo(None) -> {r}")
if r := foo(1337):
print(f"foo(1337) -> {r}")
# Example 2: while let statements
toks = iter(['a', 'b', 'c'])
while tok := next(toks, None):
print(f"{tok}")
# Example 3: list comprehension
print([tok for t in [" a", " ", " b "] 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 <patter></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) -> int:
"""Sum a and b.
>>> sum(1, 2)
3
>>> sum(10, 20)
30
"""
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 ["a ", " b"]]'
</code></pre>
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