New submission from Christian Heimes <>:

The shlex module implements simple tokenize for a shell-like mini language. The 
shlex.split() function splits a string into subcomponents just like a typical 
Unix shell. However function has a surprising feature. When None is passed into 

Note: Since the split() function instantiates a shlex instance, passing None 
for s will read the string to split from standard input.

This is both surprising, unnecessary and potentially dangerous. Reading from 
sys.stdin is a blocking operation. In case an application doesn't account for 
None, shlex.split(value) could lead to a blocked server application. I suggest 
to deprecate and eventually remove this mis-feature.

Credits: David R. MacIver reported the bug on Twitter:

messages: 315189
nosy: christian.heimes
priority: normal
severity: normal
stage: needs patch
status: open
title: Deprecate shlex.split(None) to read from stdin.
type: behavior
versions: Python 3.8

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