Python 的奇妙用法

2019 年 11 月 28 日

我从没系统地学习过 Python，我决定借此契机总结一下我个人不常用的 Python 技巧，以备后用。

Python

Decorator

def release(func):
    def inner(pokemon):
        print "Release pokemon!"
        func(pokemon)
        print "Pokemon is released!"
    return inner

@release
def getPokemon(pokemon):
    print pokemon + "!"

getPokemon("Pikachu")

Special Function Parameters

def listPokemons(*args, **kwargs):
    print "Pokemons with unknown type:"
    print args
    print "Pokemons with type:"
    print kwargs

listPokemons("Pikachu", "Eevee", dragon="Dratini", ghost="Gengar")

$ python test.py
Pokemons with unknown type:
('Pikachu', 'Eevee')
Pokemons with type:
{'ghost': 'Gengar', 'dragon': 'Dratini'}

Generator

# Using the generator pattern (an iterable)
class firstn(object):
    def __init__(self, n):
        self.n = n
        self.num, self.nums = 0, []

    def __iter__(self):
        return self

    # Python 3 compatibility
    def __next__(self):
        return self.next()

    def next(self):
        if self.num < self.n:
            cur, self.num = self.num, self.num+1
            return cur
        else:
            raise StopIteration()

sum_of_first_n = sum(firstn(1000000))

Lambda Expression

x = lambda a, b, c : a + b + c
print x(5, 6, 2)

Testing Library

import unittest

class TestStringMethods(unittest.TestCase):
    def test_upper(self):
        self.assertEqual('foo'.upper(), 'FOO')

    def test_isupper(self):
        self.assertTrue('FOO'.isupper())
        self.assertFalse('Foo'.isupper())

    def test_split(self):
        s = 'hello world'
        self.assertEqual(s.split(), ['hello', 'world'])
        # check that s.split fails when the separator is not a string
        with self.assertRaises(TypeError):
            s.split(2)

if __name__ == '__main__':
    unittest.main()