Reading a text file from standard input using <

Question

I have a Python script which ends the following way:

if __name__ == "__main__":
     if len(sys.argv) == 2:
       file = open(sys.argv[1])
       text = file.readline()
       ... #more statements

This works when I type in the following: $ python3 script.py my_file.txt

However, I want to change it so my script can accept text from standard input (or even a text file). This is what I want to be able to do:

$ ./script.py < my_file.txt

I think I need to use sys.stdin.read() (or maybe sys.stdin.readlines()). Could you tell me what I would need to change from my original script?

I'm sorry if this looks very basic, but I'm new to Python and I find it hard to see the difference.

Matthieu Brucher · Accepted Answer · 2018-11-09 18:06:30Z

1

It's exactly what you said, you don't need to open a file.

Instead of calling file.readline(), call sys.stdin.readline().

You can make it "nice", with something like:

file = sys.stdin if use_stdin else open(sys.argv[1])

answered Nov 9, 2018 at 18:06

Matthieu Brucher

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2 Comments

Me All Over a year ago

Would I still need to leave if len(sys.argv) == 2:? Or can I delete this part?

Matthieu Brucher Over a year ago

It may be that the flag use_stdin should be len(sys.argv) != 2 ;) The flag should be whatever you need to decide between file input or standard input.

LeKhan9 · Accepted Answer · 2018-11-09 18:09:29Z

0

Theres a cool module you can use for this! Assuming you want to do processing per line:

import fileinput

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

answered Nov 9, 2018 at 18:09

LeKhan9

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