Run python code with sys.stdin using my own inputs

Question

Hi I have a very naive question.

I have this piece of python code test.py that I am trying to test run. May I know how do I run it using my own inputs?

I tried running it on my command line using python3 test.py ABCD but the command line does not return anything..

I have also tried python3 test.py ABCD.txt where ABCD.txtcontains the line ABCD but also to no avail...

Any help would be greatly appreciated, thank you.

import sys
output = []
for ln in sys.stdin:
   for c in ln:
      if c in 'ABCD':
           output.append(c)
sys.stdout.write(''.join(output) + '\n')

Or python3 test.py <<<'ABCD', if you only want one line of input. Or echo ABCD | python3 test.py, or... etc, etc etc. — Charles Duffy
– Charles Duffy, Commented Aug 31, 2022 at 16:19

beepboopbeep · Accepted Answer · 2022-08-31 16:19:18Z

1

python3 test.py < ABCD.txt as suggested by keith works, thank you everyone!

answered Aug 31, 2022 at 16:19

beepboopbeep

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Comments

ARK1375 · Accepted Answer · 2022-08-31 16:22:35Z

0

Running the code like python code.py a b c d will result in storing a, b, c, and d as input command line arguments. So to handle that you need to use sys.argv and edit the code as follows.

import sys
output = []
for ln in sys.argv:
   for c in ln:
      if c in 'ABCD':
           output.append(c)
sys.stdout.write(''.join(output) + '\n')

check here for more info.

However, all standard inputs to an application are handled using < command. Just like the standard output which is handled by >. So to run the just add < like :python3 test.py < ABCD and it should be ok.

edited Aug 31, 2022 at 16:22

answered Aug 31, 2022 at 16:04

ARK1375

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2 Comments

chepner Over a year ago

Modifying the code may not be an option. The question is how to provide standard input, not how to avoid reading standard input.

beepboopbeep Over a year ago

thank you for the suggestion! ya unfortunately modifying the code is not an option, is there a way to run this code without changing it?

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