Description

DavidNemeskey

opened on May 12, 2022

Issue body actions

Bug report

If stderr is redirected, input() doesn't print the prompt. The same happens when stdout is redirected, but that is to be expected.

Code (in test.py):

x = input('prompt: ')
print(x)

When run:

> python test.py
prompt: text
text

> python test.py >out
text

> python test.py 2>err
text
text

The contents of out and err, respectively:

# out
prompt: text
# err
prompt: 

The first and second cases are as expected. In the last case, the prompt is not printed, even though it should go into stdout, according to the documentation. Instead, it is printed to err.

Your environment

• CPython versions tested on: 3.9.2
• Operating system and architecture: Linux 5.11.0-40-generic [backport to 2.7] Change documentation's Show Source link to GitHub #44~20.04.2-Ubuntu SMP Tue Oct 26 18:07:44 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

Activity

1. DavidNemeskey

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on May 12, 2022
2. DavidNemeskey

   changed the title [-]input() doesn't print anything if stderr is redirected[/-] [+]input() doesn't print the prompt if stderr is redirected[/+] on May 12, 2022
3. sweeneyde commented on May 12, 2022

   

   sweeneyde

   on May 12, 2022

   Member

   More actions

   This is probably a duplicate of:

   • Change input() to always prompt to stderr #46221

   Also related:

   • Please add argument to override stdin/out/err in the input builtin #75784
4. DavidNemeskey commented on May 12, 2022

   

   DavidNemeskey

   on May 12, 2022

   Author

   More actions

   I checked the first issue superficially, and I am not really sure it is a duplicate. Eryk's answer in the thread referenced in the penultimate comment, on the other hand, might explain what I have experienced (out is not a TTY, while the terminal is).

   So in a sense this might be duplicate (of the thread at least), but the second last comment on that is from 6 years ago, so I don't know if that issue is considered being "alive".
5. headst1337 commented on Oct 15, 2024

   

   headst1337

   on Oct 15, 2024

   More actions

   To fix this you can import readline
   For example:

   ipanov@archlinux ~/u/sandbox > cat test_stderr.py
   
   input_msg = input('Enter text: ')
   print(input_msg)
   
   ipanov@archlinux ~/u/sandbox > python test_stderr.py 2>> out.txt
   123
   123
   ipanov@archlinux ~/u/sandbox >

   and with fix:

   ipanov@archlinux ~/u/sandbox > cat test_stderr.py
   
   import readline
   
   input_msg = input('Enter text: ')
   print(input_msg)
   
   ipanov@archlinux ~/u/sandbox > python test_stderr.py 2>> out.txt
   Enter text: 123
   123
   ipanov@archlinux ~/u/sandbox >
6. DavidNemeskey commented on Oct 16, 2024

   

   DavidNemeskey

   on Oct 16, 2024

   Author

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   @headst1337 Thank you; it's good to know that readline fixes the problem. However, I think the default behavior is wrong so this is more like a workaround. Also, I couldn't find any mention of this effect in the documentation either, so that should be updated as well, depending on how this ticket is resolved.

   Reacted by Ivan Panov
7. StanFromIreland

   closed this as a duplicateof Change input() to always prompt to stderr #46221 on May 16, 2026

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