# Python 技巧

# Python 技巧       ##### Github地址：[https://github.com/vimiix/python_tricks](https://github.com/vimiix/python_tricks) ##### Slide链接：[http://vimiix.com/python_tricks](http://vimiix.com/python_tricks)   ``` Vimiix 2017.12.20 ```       --- class: inverse ## 多种方法来验证多条件语句   ``` x, y, z = 0, 1, 0   if x == 1 or y == 1 or z == 1: print('passed')   if 1 in (x, y, z): print('passed')   # These only test for truthiness: if x or y or z: print('passed')   if any((x, y, z)): print('passed')   ``` --- class: inverse ## 函数参数解包   ``` # Function argument unpacking   def myfunc(x, y, z): print(x, y, z)   tuple_vec = (1, 0, 1) dict_vec = {'x': 1, 'y': 0, 'z': 1}   myfunc(*tuple_vec) # 1, 0, 1   myfunc(**dict_vec) # 1, 0, 1   ``` --- class: inverse ## 使用timeit模块来测试函数执行效率   ``` import timeit   rt = timeit.timeit('"-".join(str(n) for n in range(100))', number=10000) print(rt) # 0.252703905106   rt = timeit.timeit('"-".join([str(n) for n in range(100)])', number=10000) print(rt) # 0.234980106354   rt = timeit.timeit('"-".join(map(str, range(100)))', number=10000) print(rt) # 0.152318954468   ``` --- class: inverse ## 合并两个字典在不同版本中的写法   ``` x = {'a': 1, 'b': 2} y = {'b': 3, 'c': 4}   # Python 3.5+ z = {**x, **y} print(z) # {'c': 4, 'a': 1, 'b': 3}   # Python 2.x z = dict(x, **y) print(z) # {'a': 1, 'c': 4, 'b': 3} ``` --- class: inverse ## 巧用json模块更舒服的打印字典   ``` # 标准打印出来，对于阅读不是很友好 my_mapping = {'a': 23, 'b': 42, 'c': 0xc0ffee} print(my_mapping) # {'b': 42, 'c': 12648430. 'a': 23} # đŸ˜ž   # 使用json可以更好的展示 import json print(json.dumps(my_mapping, indent=4, sort_keys=True)) # { # "a": 23, # "b": 42, # "c": 12648430 # }   ``` --- class: inverse ## 通过字典的值(value)排序输出   ``` # How to sort a Python dict by value   xs = {'a': 4, 'b': 3, 'c': 2, 'd': 1}   print(sorted(xs.items(), key=lambda x: x[1])) # [('d', 1), ('c', 2), ('b', 3), ('a', 4)]   # Or:   import operator print(sorted(xs.items(), key=operator.itemgetter(1))) # [('d', 1), ('c', 2), ('b', 3), ('a', 4)] ``` --- class: inverse ## 字典的get用法和默认值   ``` name_for_userid = { 382: "Alice", 590: "Bob", 951: "Dilbert", }   def greeting(userid): return "Hi %s!" % name_for_userid.get(userid, "there")   print(greeting(382)) # "Hi Alice!"   print(greeting(2333333)) # "Hi there!" ``` --- class: inverse ## 用namedtuple来代替简单的类   ``` from collections import namedtuple Car = namedtuple('Car', 'color mileage')   # 实例化一个Car,并像类一样使用 my_car = Car('red', 3812.4) print(my_car.color) # 'red' print(my_car.mileage) # 3812.4   print(my_car) # Car(color='red' , mileage=3812.4)   # 就像元组一样，namedtuple也不可更改: my_car.color = 'blue' # AttributeError: "can't set attribute" ``` --- class: center, middle, inverse ## 持续更新中... --- class: middle, inverse ## 联系方式 ###   - Website: http://vimiix.com   - Twitter: http://twitter.com/_vimiix   - GitHub: http://github.com/vimiix   - Email: [[e-mail]](mailto:[e-mail])