【python学习笔记】列表、元组和字典的迭代

在python中，列表和元组的迭代是通过for....in....来完成的；

>>> a=[1,2,3,4,5,6,7]
>>> for index in a:
...  print(index)
...
1
2
3
4
5
6
7
>>>
>>>> b=(11,22,33)
>>> for i in b:
...  print(i)
...
11
22
33
>>> c=set("abcd")
>>> for i in c:
...  print(i)
...
d
b
a
c
>>> d={'a':1,'b':2,'c':3}
>>> for i in d:
...  print(i)
...
a
b
c
>>> for ch in 'ABC':
...  print(ch)
...
A
B
C

对于列表、元组和集合这种就OK，但是字典有键值对，那么对于key的迭代和value的迭代就不一样了，keys()可以获取所有的键，values()可以获取所有的值，items()就是获取所有的键值对了，范例如下：

>>> for i in d.keys():
...  print(i)
...
a
b
c
>>> for value in d.values():
...  print(value)
...
1
2
3
>>> for key in d.keys():
...  print(key+"-"+str(d.get(key)))
...
a-1
b-2
c-3
>>> for key,value in d.items():
...  print(key+":"+str(value))
...
a:1
b:2
c:3