Python - Removing tuples by prefix and suffix from list

What's the fastest way to remove tuples from a python list (and update the list with the removed tuples) according to what the tuple starts with or ends with.

Example:

import itertools
l1 = ["a", "b", "c"]
l2 = ["d", "e", "f"]
tupl_lst = list(itertools.product(l1, l2))
tupl_lst
Out[42]:
[('a', 'd'),
('a', 'e'),
('a', 'f'),
('b', 'd'),
('b', 'e'),
('b', 'f'),
('c', 'd'),
('c', 'e'),
('c', 'f')]


I want to remove all tuples that starts with 'a' OR ends with 'f' so that my output will look as follows:

'a'

'f'

[('b', 'd'),
('b', 'e'),
('c', 'd'),
('c', 'e')]


What is the fastest way to do it ?

3 Answers
3

with a list comprehension:

[t for t in tupl_lst if t[0]!='a' and t[1]!='f']


with filter:

filter

list(filter(lambda t: t[0]!='a' and t[1]!='f',tupl_lst))


You can even skip the itertools.product()and just use one list-comprehension:

itertools.product()

l1 = ["a", "b", "c"]
l2 = ["d", "e", "f"]

tupl_lst = [(x, y) for x in l1 for y in l2 if x!="a" and y!="f"]

#output
[('b', 'd'), ('b', 'e'), ('c', 'd'), ('c', 'e')]


Avoid the prefix (a) and suffix (f) altogether by iterating over slices of the lists.

a

f

[(x, y) for x in l1[1:] for y in l2[:-1]]
# [('b', 'd'), ('b', 'e'), ('c', 'd'), ('c', 'e')]


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