python 读文件 和行号

python 读文件 和行号 代码如下：

file = open('file.txt','r')
for (num,value) in enumerate(file):
    print "line num is: ",num,"content:",value
file.close()

with open('file.txt','r') as f:

for (num,value) in enumerate(file):

print "line num is: ",num,"content:",value
 
-------output---------
line number is:  0 content: start line
 
line number is: 1 content:  test
 
line number is: 2 content: end