In its __init__ method, shlex.shlex sets self.debug = 0. An `if self.debug:` statement follows shortly thereafter and without allowing the user to change self.debug.

The code inside the if statement is unreachable. Users should either be permitted to set debug on via an optional __init__ parameter, or debug should be taken out of the initializer altogether.

Hat tip abarnert on StackOverflow for digging in.

http://stackoverflow.com/questions/29996208/putting-shlex-in-debug-mode

This code was introduced in https://hg.python.org/cpython/rev/81a121d21340

Thanks for the report.

> Users should either be permitted to set debug on via an optional __init__ parameter,

This is already possible via the debug attribute (https://docs.python.org/3/library/shlex.html#shlex.shlex.debug), so I don't think adding a debug parameter to __init__ is necessary.

> or debug should be taken out of the initializer altogether.

+1. We can just remove the unreachable code.

Presumably ESR thought that information was useful enough to send Guido a patch to add it. But apparently nobody's missed it in the 15 years it's been checked in but unreachable. If anyone needed to know the `instream` and `lineno` right after initialization, presumably they just printed them directly. So, yeah, seems unnecessary to me.

New changeset 395e190ead36 by Raymond Hettinger in branch 'default':
Issue #24113:  Remove unreachable code in shlex.
https://hg.python.org/cpython/rev/395e190ead36