Python enumerate函数

enumerate函数接受一个可遍历的对象，如列表、字符串，可同时遍历下标（index）及元素值（value）

>>> a = [‘aaa‘,‘bbb‘,‘ccc‘,1235]
>>> print(a)
[‘aaa‘, ‘bbb‘, ‘ccc‘, 1235]
>>> print(len(a))
4
>>> for i in range(len(a)):
    print(i)

0
1
2
3
>>> for j in range(len(a)):
    print(j,a[j])

0 aaa
1 bbb
2 ccc
3 1235
>>> for i,j in enumerate(a):
    print(i,j)

0 aaa
1 bbb
2 ccc
3 1235
>>> for x in enumerate(a):
    print(x)

(0, ‘aaa‘)
(1, ‘bbb‘)
(2, ‘ccc‘)
(3, 1235)
>>> 

使用enumerate函数来统计文本行数：

文本内容：test.txt

this
is
a
test

代码：

>>> for count,line in enumerate(open(r‘I:\PythonTest\1234.txt‘,‘r‘)):
    count +=1

>>> print(count)
4
>>> 

实例2：

文本内容：1234.txt

The Zen of Python, by Tim Peters

Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
Special cases aren‘t special enough to break the rules.
Although practicality beats purity.
Errors should never pass silently.
Unless explicitly silenced.
In the face of ambiguity, refuse the temptation to guess.
There should be one-- and preferably only one --obvious way to do it.
Although that way may not be obvious at first unless you‘re Dutch.
Now is better than never.
Although never is often better than *right* now.
If the implementation is hard to explain, it‘s a bad idea.
If the implementation is easy to explain, it may be a good idea.
Namespaces are one honking great idea -- let‘s do more of those!

代码：

>>> for count,line in enumerate(open(r‘I:\PythonTest\1234.txt‘,‘r‘)):
	count +=1
	print(count,line)

结出结果：
1 The Zen of Python, by Tim Peters
2
3 Beautiful is better than ugly.
4 Explicit is better than implicit.
5 Simple is better than complex.
6 Complex is better than complicated.
7 Flat is better than nested.
8 Sparse is better than dense.
9 Readability counts.
10 Special cases aren‘t special enough to break the rules.
11 Although practicality beats purity.
12 Errors should never pass silently.
13 Unless explicitly silenced.
14 In the face of ambiguity, refuse the temptation to guess.
15 There should be one-- and preferably only one --obvious way to do it.
16 Although that way may not be obvious at first unless you‘re Dutch.
17 Now is better than never.
18 Although never is often better than *right* now.
19 If the implementation is hard to explain, it‘s a bad idea.
20 If the implementation is easy to explain, it may be a good idea.
21 Namespaces are one honking great idea -- let‘s do more of those!
>>>