Python input is restricted when executed from a batch file within a conditional statement and following a timeout period

Question

Python input is restricted when executed from a batch file within a conditional statement and following a timeout period

Here is a simple working example:

test.bat:

@echo off
if 0==0 (
  timeout 3
  python test.py
)

test.py:

input('press ENTER to exit')

In cmd.exe:

call test.bat
> Waiting for 0 seconds, press a key to continue ...
> press ENTER to exit_

However, the script gets stuck at the input statement. If I keep pressing enter, it will eventually raise an exception:

Traceback (most recent call last):
  File "test.py", line 1, in <module>
    input('press ENTER to exit')
OSError: [WinError 8] Not enough storage is available to process this command

This issue occurred on Windows 7 SP1 while testing with various Python versions:

Python 3.6 (64-bit)
Python 3.6 (32-bit)
Python 3.5 (32-bit)
Python 2.7 (32-bit) - in this case, the script remains stuck without raising an exception

If anyone can replicate this problem or has any insights into what might be causing it, please let me know!

python batch-file

Answer 1

Answer №1

The issue can be replicated on Windows 7 using Python 3.6.5 64 bit.

Here are a few alternatives to work around the problem with timeout:

@echo off
if 0==0 (
  echo Pause for 3 seconds
  ping -n 3 localhost >nul
  python test.py
)
exit /b

This method utilizes ping, which does not cause any issues.

@echo off
if 0==0 (
  timeout 3
  call :run_python test.py
)
exit /b

:run_python
python %*
exit /b

With this approach, a label named :run_python is used, allowing the interpreter to execute Python code outside of the parentheses. Any arguments provided after calling the label will be forwarded to python.

Answer 2

The issue can be replicated on Windows 7 using Python 3.6.5 64 bit.

Here are a few alternatives to work around the problem with timeout:

@echo off
if 0==0 (
  echo Pause for 3 seconds
  ping -n 3 localhost >nul
  python test.py
)
exit /b

This method utilizes ping, which does not cause any issues.

@echo off
if 0==0 (
  timeout 3
  call :run_python test.py
)
exit /b

:run_python
python %*
exit /b

With this approach, a label named :run_python is used, allowing the interpreter to execute Python code outside of the parentheses. Any arguments provided after calling the label will be forwarded to python.

Answer 3

Answer №2

Indeed, the behavior you noted can be replicated on Windows 7 using Python 2.6 and Python 2.7, but not on Windows 10 with Python 2.7. The differences in file sizes of timeout.exe between Windows 7 and Windows 10 indicate changes to that command.

It appears that timeout may manipulate the file pointer in the STD_IN stream (handle 0), especially when adjusting the countdown display (referencing this thread: Clear a line/move the cursor, using the Timeout command or similar).

The issue is not limited to interactions with the if command; it arises as soon as both timeout and the Python script call are within the same block of code:

(
    timeout 3
    python test.py
)

A similar problem occurs when they are in the same line:

timeout 3 & python test.py

However, if these two commands are separated onto different lines without parentheses, they function correctly:

timeout 3
python test.py

Replacing the timeout command with pause, which also reads from STD_IN, resolves the issue smoothly:

(
    pause
    python test.py
)

Alternatively:

pause & python test.py

michael_heath provided a helpful workaround in his answer utilizing ping. Nevertheless, unlike timeout, this method lacks the ability to be stopped by a key press (making it comparable to timeout 3 /NOBREAK).

Answer 4

Indeed, the behavior you noted can be replicated on Windows 7 using Python 2.6 and Python 2.7, but not on Windows 10 with Python 2.7. The differences in file sizes of timeout.exe between Windows 7 and Windows 10 indicate changes to that command.

It appears that timeout may manipulate the file pointer in the STD_IN stream (handle 0), especially when adjusting the countdown display (referencing this thread: Clear a line/move the cursor, using the Timeout command or similar).

The issue is not limited to interactions with the if command; it arises as soon as both timeout and the Python script call are within the same block of code:

(
    timeout 3
    python test.py
)

A similar problem occurs when they are in the same line:

timeout 3 & python test.py

However, if these two commands are separated onto different lines without parentheses, they function correctly:

timeout 3
python test.py

Replacing the timeout command with pause, which also reads from STD_IN, resolves the issue smoothly:

(
    pause
    python test.py
)

Alternatively:

pause & python test.py

michael_heath provided a helpful workaround in his answer utilizing ping. Nevertheless, unlike timeout, this method lacks the ability to be stopped by a key press (making it comparable to timeout 3 /NOBREAK).

Python input is restricted when executed from a batch file within a conditional statement and following a timeout period

Answer №1

Answer №2

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