python笔记---集合迭代技术

dongfangho

>>> basket = ['apple', 'orange', 'apple', 'pear', 'orange', 'banana']
>>> for f in sorted(set(basket)):
...     print(f)
...
apple
banana
orange
pear

 　　集合迭代技术
　　使用字典对象的items()方法可以得到键值对序列。

>>> knights = {'gallahad': 'the pure', 'robin': 'the brave'}
>>> for k, v in knights.items():
...     print(k, v)
...
gallahad the pure
robin the brave

　　使用方法enumerate()可以得到序列的下标和值得序列。

>>> for i, v in enumerate(['tic', 'tac', 'toe']):
...     print(i, v)
...
0 tic
1 tac
2 toe

　　可以通过zip（）方法同时迭代多个序列。

>>> questions = ['name', 'quest', 'favorite color']
>>> answers = ['lancelot', 'the holy grail', 'blue']
>>> for q, a in zip(questions, answers):
...     print('What is your {0}?  It is {1}.'.format(q, a))
...
What is your name?  It is lancelot.
What is your quest?  It is the holy grail.
What is your favorite color?  It is blue.

　　可以同个reversed()翻转一个序列。

>>> for i in reversed(range(1, 10, 2)):
...     print(i)
...
9
7
5
3
1

　　通过sorted（）可以排序一个序列。