Searching a 2-Dimensional Tuple/List in Python

Question

I want to search a tuple of tuples for a particular string and return the index of the parent tuple. I seem to run into variations of this kind of search frequently.

What is the most pythonic way to do this?

I.E:

derp = (('Cat','Pet'),('Dog','Pet'),('Spock','Vulcan'))
i = None
for index, item in enumerate(derp):
    if item[0] == 'Spock':
         i = index
         break
>>>print i
2

I could generalize this into a small utility function that takes an iterable, an index (I've hard coded 0 in the example) and a search value. It does the trick but I've got this notion that there's probably a one-liner for it ;)

I.E:

def pluck(iterable, key, value):
    for index, item in enumerate(iterable):
        if item[key] == value:
             return index
    return None

Answer 1

Lambdas are fun!

return reduce(
    lambda x,(i,(a,b)): i,
    filter(
        lambda (i,(a,b)): a == "Spock",
        enumerate(depr)
    ),
    None
)

Answer 2

It does the trick but I've got this notion that there's probably a one-liner for it ;)

The one-liner is probably not the pythonic way to do it :)

The method you have used looks fine.

Edit:

If you want to be cute:

return next( (i for i,(k,v) in enumerate(items) if k=='Spock'),None)

next takes a generator expression and returns the next value or the second argument (in this case None) once the generator has been exhausted.

Answer 3

If you're often searching the same tuple, you can build a dict.

lookup_table = dict((key, i) for i, (key, unused) in enumerate(derp))

print lookup_table['Spock']
--> 2