What is the encoding of CompletedProcess.stdout coming from Powershell/Windows in Python?

Question

I am getting this output from a ping request started from Python with subprocess.run():

>>> process.stdout
b"rnEnvoi d'une requx88te 'ping' sur www.google.fr [142.250.179.195] avec 32 octets de donnx82esxff:rnRx82ponse de 142.250.179.195xff: octets=32 temps=39 ms TTL=110rnRx82ponse de 142.250.179.195xff: octets=32 temps=46 ms TTL=110rnRx82ponse de 142.250.179.195xff: octets=32 temps=37 ms TTL=110rnrnStatistiques Ping pour 142.250.179.195:rn    Paquetsxff: envoyx82s = 3, rex87us = 3, perdus = 0 (perte 0%),rnDurx82e approximative des boucles en millisecondes :rn    Minimum = 37ms, Maximum = 46ms, Moyenne = 40msrn"

I run this script from Pycharm that runs Powershell on a Windows 10 21H2 in French language. So I expect encoding Windows-1252. Which is also the guess of chardet:

>>> chardet.detect(process.stdout)
{'encoding': 'Windows-1252', 'confidence': 0.73, 'language': ''}

However decoding this with Windows-1252 does not look very right:

>>> process.stdout.decode("windows-1252")
"rnEnvoi d'une requˆte 'ping' sur www.google.fr [142.250.179.195] avec 32 octets de donn‚esÿ:rnR‚ponse de 142.250.179.195ÿ: octets=32 temps=39 ms TTL=110rnR‚ponse de 142.250.179.195ÿ: octets=32 temps=46 ms TTL=110rnR‚ponse de 142.250.179.195ÿ: octets=32 temps=37 ms TTL=110rnrnStatistiques Ping pour 142.250.179.195:rn    Paquetsÿ: envoy‚s = 3, re‡us = 3, perdus = 0 (perte 0%),rnDur‚e approximative des boucles en millisecondes :rn    Minimum = 37ms, Maximum = 46ms, Moyenne = 40msrn"

0x88 should be ê and 0x82 should be è

Asked By: courrier

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Source

Answer 1

Console applications on Windows typically use the console’s active code page to encode their output, which by default is the system’s legacy OEM code page (e.g., CP437 on US-English systems), not the legacy ANSI code page used by GUI applications (e.g, Windows-1252):

You can use the following code to determine the console’s active code page and decode based on it:

import ctypes
import subprocess

# Get the console's active code page, as an integer.
oemCP = ctypes.windll.kernel32.GetConsoleOutputCP()

process = subprocess.run('ping.exe', capture_output=True)

# Decode based on the console's active code page.
print(process.stdout.decode("cp" + str(oemCP)))

A note re detecting the coding:

The prevalent single-byte code pages that are used as the OEM and ANSI code pages do not use BOMs, and any byte value is also a valid character.
This ultimately makes any attempt to detect what an unknown encoding is guesswork – though the probability of guessing right can be improved with sophisticated linguistic analysis.
I don’t know what approach chardet.detect() uses, but in this case it guessed incorrectly; that it guessed can be inferred from the presence of a confidence value.

0x88 should be ê and 0x82 should be è

This actually applies to CP437, not to Windows-1252, as the following PowerShell code demonstrates:

PS> [System.Text.Encoding]::GetEncoding(437).GetString([byte[]] (0x88, 0x82))

êé

Answered By: mklement0

Answer 2

If any one lands here, small working snipped based on mklement0 answer.

import locale
import ctypes
import subprocess

oemCP = ctypes.windll.kernel32.GetConsoleOutputCP()
print(f'{locale.getpreferredencoding()=}')

encoding = "cp" + str(oemCP)
print(f"{encoding=}")

p = subprocess.run('dir c:\',
                   shell=True,
                   stdout=subprocess.PIPE,
                   universal_newlines=True,
                   encoding=encoding,
                   stderr=subprocess.STDOUT)

print(p.stdout)

Answered By: Andrzej O

What is the encoding of CompletedProcess.stdout coming from Powershell/Windows in Python?

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