list comprehensions列表解析

没有使用列表解析：

1 x =[]
2 for i in (1, 2, 3):
3     x.append(i)
4
5 """
6 >>> x
7 [1, 2, 3]
8 """

列表解析式:

1 x = [i for i in (1, 2, 3)]
2 """
3 >>> x
4 [1, 2, 3]
5 """

多重列表解析：

 1 x = [word.capitalize()
 2      for line in ("hello world?", "world!", "or not")
 3      for word in line.split()#空格分割
 4      if not word.startswith("or")]
 5
 6 """
 7 >>> x
 8 [‘Hello‘, ‘World?‘, ‘World!‘, ‘Not‘]
 9
10 """

创建一个字典和集合的方法也是一样的：

1 >>> {x: x.upper() for x in [‘hello‘, ‘world‘]}
2 {‘world‘: ‘WORLD‘, ‘hello‘: ‘HELLO‘}
3
4 >>> {x.upper() for x in [‘hello‘, ‘world‘]}
5 set([‘WORLD‘, ‘HELLO‘])
6 >>>