input()    #返回能够用于for循环遍历的对象
filename()  #返回当前文件的名称
lineno()   #返回当前已经读取的行的数量（或者序号）
filelineno() #返回当前读取的行的行号
isfirstline() #检查当前行是否是文件的第一行

# cat > test.txt << EOF
Hello,Python
www.jb51.net
This is a test file
EOF

#!/usr/bin/env python
import fileinput
for line in fileinput.input('test.txt',backup='_bak',inplace=1):
  print line.replace('Python','LinuxEye'),
fileinput.close()

# python file_input.py #执行file_input.py
# ls test.txt*
test.txt test.txt_bak
 
# cat test.txt
Hello,LinuxEye
www.jb51.net
This is a test file
 
# cat test.txt_bak
Hello,Python
www.jb51.net
This is a test file

> import fileinput
> for line in fileinput.input('test.txt'):
...   print fileinput.filename(),fileinput.lineno(),fileinput.filelineno()
...
test.txt 1 1
test.txt 2 2
test.txt 3 3

> import fileinput
> for line in fileinput.input('test.txt'):
...   if fileinput.isfirstline():
...     print line,
...   else:
...     break
...
Hello,LinuxEye