Partitioning a list based on values in tuples - Python

What is the best way to go about partitioning a list of tuples in python?

Currently I have a sorted list of tuples, by the second element (a value), and I want to find all values that are repeated at the be开发者_高级运维ginning in an efficient manner.

say:

[ ("tearing", 3), ("me", 3), ("apart", 3), ("lisa", 3), 
  ("denny", 0), ("mark",0) ]

Running it through the function would return

[("tearing", 3), ("me", 3), ("apart", 3), ("lisa", 3)]. 

But I am not sure how to go about this.

import itertools
import operator

L = [("tearing", 3), ("me", 3), ("apart", 3), ("lisa", 3), ("denny", 0), ("mark",0)]

print list(itertools.groupby(L, operator.itemgetter(1)).next()[1])

# [('tearing', 3), ('me', 3), ('apart', 3), ('lisa', 3)]

But really, there was no need to remind me about that movie.

from itertools import takewhile

L = [("tearing", 3), ("me", 3), ("apart", 3), ("lisa", 3), ("denny", 0), ("mark",0)]
first = L[0][1]

print list(takewhile(lambda x : x[1] == first, L))

a little variant of ignacio's

An alternative to @Ignacio Vazquez-Abrams' answer, using list comprehensions:

>>> data=[ ("tearing", 3), ("me", 3), ("apart", 3), ("lisa", 3), ("denny", 0), ("mark",0) ]
>>> print [x for x in data if x[-1]== data[0][-1]]
[('tearing', 3), ('me', 3), ('apart', 3), ('lisa', 3)]