[Tutor] Finding Match in nexted tuple
dyoo at hkn.eecs.berkeley.edu
Thu Apr 22 13:16:34 EDT 2004
On Wed, 21 Apr 2004, Tim Johnson wrote:
> * Magnus Lycka <magnus at thinkware.se> [040421 17:04]:
> > Tim Johnson wrote:
> > > Let's say I have a list of zip codes returned from a MySQLdb query
> > > zip_code_list = (('84536',), ('85003',), ('85004',), ('85006',),
> > > ('85007',), ('85008',))
> > > # and I want to look for a match for a value like '85004'
> > If you know that the format is exactly like that, you can
> > simply do:
> > if ('85004',) in zip_code_list:
> > print "Found!"
> Good tip..
> > ..but maybe that's not what you intended? If '85004' might
> > just be in an arbitrary position in a sequence of tuples with
> > more columns than the zip codes, you could for instance do:
> > if '85004' in str(zip_code_list):
> > print "Found!"
> Eureka! That's what I meant by a 'pythonesque' solution.
Be wary of string solutions. In this particular case, a string-search
approach will work because we're assuming fixed-width, comma-delimited
zip-code data. In the general case, we have to be careful, because the
'in' check on strings is a "substring' check.
Not only is something like:
'hello' in 'hello world'
'or' in 'hello world'
is also True. That's why string-searching approaches to lookup can be
I suspect that the first approach that Magnus suggested,
if ('85004',) in zip_code_list: ...
is probably faster than the str() approach, but I have no empirical data
yet to back my guesses. *grin* But I'd feel more secure about using this,
as opposed to "if '85004' in str(zip_code_list): ...".
Both approaches, though, use a linear scan through 'zip_code_list'. If
your list is long, and if you plan to do repeated searches, then you may
want to later look into 'sets':
as they allow us to look things up more efficiently than in the two
Hope this helps!
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