Python equivalent of Perl's while (<>) {...}?

Question

I write a lot of little scripts that process files on a line-by-line basis. In Perl, I use

while (<>) {
    do stuff;
}

This is handy because it doesn't care where the input comes from (a file or stdin).

In Python I use this

if len(sys.argv) == 2: # there's a command line argument
    sys.stdin = file(sys.argv[1])
for line in sys.stdin.readlines():
    do stuff

which doesn't seem very elegant. Is there a Python idiom that easily handles file/stdin input?

Answer 1

The fileinput module in the standard library is just what you want:

import fileinput

for line in fileinput.input(): ...

Answer 2

import fileinput
for line in fileinput.input():
    process(line)

This iterates over the lines of all files listed in sys.argv[1:], defaulting to sys.stdin if the list is empty.

Answer 3

fileinput defaults to stdin, so would make it slightly more concise.

If you do a lot of command-line stuff, though, this piping hack is very neat.