How do you read from stdin?

Question

I\'m trying to do some of the code golf challenges, but they all require the input to be taken from stdin. How do I get that in Python?

Answer 1

The problem I have with solution

import sys

for line in sys.stdin:
    print(line)

is that if you don't pass any data to stdin, it will block forever. That's why I love this answer: check if there is some data on stdin first, and then read it. This is what I ended up doing:

import sys
import select

# select(files to read from, files to write to, magic, timeout)
# timeout=0.0 is essential b/c we want to know the asnwer right away
if select.select([sys.stdin], [], [], 0.0)[0]:
    help_file_fragment = sys.stdin.read()
else:
    print("No data passed to stdin", file=sys.stderr)
    sys.exit(2)