python 3: TypeError: a bytes-like object is required, not 'str'

python 3: TypeError: a bytes-like object is required, not 'str' - Printable Version

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python 3: TypeError: a bytes-like object is required, not 'str' - wardancer84 - Jul-09-2021

hey all,

i know this might be a dull question, but i dont get it...

this works in python2

#!/usr/bin/env python

import subprocess

proclist = subprocess.check_output(['ps', 'uaxw']).splitlines()
cfeagent_procs = [proc for proc in proclist if 'cf-agent' in proc]
cfeagent_count = len(cfeagent_procs)
print(cfeagent_count)
if cfeagent_count > 10:
    print("agents high")

Output:root@aixhemadbprc2: /root # ./process_count.py
145
agents high

but not in python3

Error:root@aixhemadbprc2: /root # ./process_count.py
Traceback (most recent call last):
  File "./process_count.py", line 6, in <module>
    cfeagent_procs = [proc for proc in proclist if 'cf-agent' in proc]
  File "./process_count.py", line 6, in <listcomp>
    cfeagent_procs = [proc for proc in proclist if 'cf-agent' in proc]
TypeError: a bytes-like object is required, not 'str'

sorry i need a hint...

wbr

chris

RE: python 3: TypeError: a bytes-like object is required, not 'str' - DeaD_EyE - Jul-09-2021

subprocess.check_output(['ps', 'uaxw']).splitlines()

Will output raw bytes because the encoding is missing.
This is the default behavior.

subprocess.check_output(['ps', 'uaxw'], encoding="utf8").splitlines()

Will decode as utf8 and return a str.

Docs: https://docs.python.org/3/library/subprocess.html#subprocess.check_output

RE: python 3: TypeError: a bytes-like object is required, not 'str' - wardancer84 - Jul-09-2021

thank you!

RE: python 3: TypeError: a bytes-like object is required, not 'str' - deanhystad - Jul-09-2021

Your code worked in Python 2 because strings were made up of bytes. In Python 3 strings are made up of Unicode characters. This is a good thing, but it does mean that you'll need to encode/decode when working with legacy software that still thinks ASCII is king.