[ python-Bugs-1340337 ] time.strptime() with bad % code throws bad exception

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Bugs item #1340337, was opened at 2005-10-27 23:48
Message generated for change (Settings changed) made by bcannon
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Category: Python Library
Group: Python 2.4
>Status: Closed
>Resolution: Fixed
Priority: 5
Submitted By: Steve R. Hastings (steveha)
Assigned to: Brett Cannon (bcannon)
Summary: time.strptime() with bad % code throws bad exception

Initial Comment:
I am using Python 2.4.2, the latest version currently
available for the system I am using, which is Ubuntu
5.10 for x86.

I was calling the time.strptime() function, and I had
accidentally typed an extra % symbol in the time format
string.  If you do this you get a baffling message in
the traceback.  The deepest frame of the traceback
looks like this:

  File "/usr/lib/python2.4/_strptime.py", line 256, in
pattern
    processed_format = "%s%s%s" % (processed_format,
KeyError: '-'


This means that I accidentally put "%-" in my format
string.

What happens if I accidentally put "% " in my format
string?  This:

  File "/usr/lib/python2.4/_strptime.py", line 256, in
pattern
    processed_format = "%s%s%s" % (processed_format,
KeyError: '\'

It turns out that spaces in the format string are
replaced by r'\s*' by the time the exception happens. 
It really freaked me out to see Python complaining
about a backslash, when I hadn't put a backslash into
my format string.

I propose that this library call should be re-written
to catch the exception, and then throw a more sensible
exception, including a statement like: "unknown % code
in format string".  In a perfect world this would be
done in such a way that the last frame appearing in the
traceback would be for the call to time.strptime(), and
not show any lines from the guts of time.strptime()
about regular expression compiling.

----------------------------------------------------------------------

>Comment By: Brett Cannon (bcannon)
Date: 2005-11-02 15:05

Message:
Logged In: YES 
user_id=357491

Rev. 41376 has the fix in the trunk.  I am not going to
backport since it is a semantic change.

Thanks, Steve.

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