在字典中循环时,关键字和对应的值可以使用 iteritems() 方法同时解读出来:
>>> knights = {"gallahad": "the pure", "robin": "the brave"}
>>> for k, v in knights.items():
... print(k, v)
...
gallahad the pure
robin the brave
在序列中循环时,索引位置和对应值可以使用 enumerate() 函数同时得到:
>>> for i, v in enumerate(["tic", "tac", "toe"]):
... print(i, v)
...
0 tic
1 tac
2 toe
同时循环两个或更多的序列,可以使用 zip() 整体打包:
>>> 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.
需要逆向循环序列的话,先正向定位序列,然后调用 reversed() 函数:
>>> for i in reversed(range(1, 10, 2)):
... print(i)
...
9
7
5
3
1
要按排序后的顺序循环序列的话,使用 sorted() 函数,它不改动原序列,而是生成一个新的已排序的序列:
>>> basket = ["apple", "orange", "apple", "pear", "orange", "banana"]
>>> for f in sorted(set(basket)):
... print(f)
...
apple
banana
orange
pear