Python由于语言的简洁性，让我们以人类思考的方式来写代码，新手更容易上手，老鸟更爱不释手。
要写出 Pythonic（优雅的、地道的、整洁的）代码，还要平时多观察那些大牛代码，Github 上有很多非常优秀的源代码值得阅读，比如：requests、flask、tornado，这里小明收集了一些常见的 Pythonic 写法，帮助你养成写优秀代码的习惯。
01. 变量交换
Bad
tmp = aa = bb = tmp
Pythonic
a,b = b,a
02. 列表推导
Bad
my_list = []for i in range(10): my_list.append(i*2)
Pythonic
my_list = [i*2 for i in range(10)]
03. 单行表达式
虽然列表推导式由于其简洁性及表达性，被广受推崇。
但是有许多可以写成单行的表达式，并不是好的做法。
Bad
print 'one'; print 'two'if x == 1: print 'one'if <complex comparison> and <other complex comparison>: # do something
Pythonic
print 'one'print 'two'if x == 1: print 'one'cond1 = <complex comparison>cond2 = <other complex comparison>if cond1 and cond2: # do something
04. 带索引遍历
Bad
for i in range(len(my_list)): print(i, "-->", my_list[i])
Pythonic
for i,item in enumerate(my_list): print(i, "-->",item)
05. 序列解包
Pythonic
a, *rest = [1, 2, 3]# a = 1, rest = [2, 3]a, *middle, c = [1, 2, 3, 4]# a = 1, middle = [2, 3], c = 4
06. 字符串拼接
Bad
letters = ['s', 'p', 'a', 'm']s=""for let in letters: s += let
Pythonic
letters = ['s', 'p', 'a', 'm']word = ''.join(letters)
07. 真假判断
Bad
if attr == True: print 'True!'if attr == None: print 'attr is None!'
Pythonic
if attr: print 'attr is truthy!'if not attr: print 'attr is falsey!'if attr is None: print 'attr is None!'
08. 访问字典元素
Bad
d = {'hello': 'world'}if d.has_key('hello'): print d['hello'] # prints 'world'else: print 'default_value'
Pythonic
d = {'hello': 'world'}print d.get('hello', 'default_value') # prints 'world'print d.get('thingy', 'default_value') # prints 'default_value'# Or:if 'hello' in d: print d['hello']
09. 操作列表
Bad
a = [3, 4, 5]b = []for i in a: if i > 4: b.append(i)
Pythonic
a = [3, 4, 5]b = [i for i in a if i > 4]# Or:b = filter(lambda x: x > 4, a)
Bad
a = [3, 4, 5]for i in range(len(a)): a[i] += 3
Pythonic
a = [3, 4, 5]a = [i + 3 for i in a]# Or:a = map(lambda i: i + 3, a)
10. 文件读取
Bad
f = open('file.txt')a = f.read()print af.close()
Pythonic
with open('file.txt') as f: for line in f: print line
11. 代码续行
Bad
my_very_big_string = """For a long time I used to go to bed early. Sometimes, \ when I had put out my candle, my eyes would close so quickly that I had not even \ time to say “I'm going to sleep.”"""from some.deep.module.inside.a.module import a_nice_function, another_nice_function, \ yet_another_nice_function
Pythonic
my_very_big_string = ( "For a long time I used to go to bed early. Sometimes, " "when I had put out my candle, my eyes would close so quickly " "that I had not even time to say “I'm going to sleep.”")from some.deep.module.inside.a.module import ( a_nice_function, another_nice_function, yet_another_nice_function)
12. 显式代码
Bad
def make_complex(*args): x, y = args return dict(**locals())
Pythonic
def make_complex(x, y): return {'x': x, 'y': y}
13. 使用占位符
Pythonic
filename = 'foobar.txt'basename, _, ext = filename.rpartition('.')
14. 链式比较
Bad
if age > 18 and age < 60: print("young man")
Pythonic
if 18 < age < 60: print("young man")
理解了链式比较操作，那么你应该知道为什么下面这行代码输出的结果是 False
>>> False == False == True False
15. 三目运算
这个保留意见。随使用习惯就好。
Bad
if a > 2: b = 2else: b = 1#b = 2
Pythonic
a = 3 b = 2 if a > 2 else 1#b = 2
参考文档
http://docs.python-guide.org/en/latest/writing/style/
https://foofish.net/idiomatic_part2.html
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