What behavior would you expect?

[Jason Friedman]

I have need to search a directory and return the name of the most recent
file matching a given pattern.  Given a directory with these files and
timestamps,

q.pattern1.abc Feb 13
r.pattern1.cdf  Feb 12
s.pattern1.efg  Feb 10
t.pattern2.abc Feb 13
u.pattern2.xyz  Feb 14
v.pattern2.efg  Feb 10

calling my_function("/path/to/dir", "pattern1") will return q.pattern1.abc
and calling my_function("/path/to/dir", "pattern2") will return
u.pattern2.xyz.

My question is, what would be a reasonable behavior/result/return value if:
1. "/path/to/dir" does not exist or is not readable
2. no files match the given pattern

Also, what would be a reasonable name for such a function?
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/python-list/attachments/20150218/a71249d6/attachment.html>