If i have two lists:
a = [1,2,1,2,4] and b = [1,2,4]
how do i get
a - b = [1,2,4]
such that one element from b removes only one element from a if that element is present in a.
Asked
Active
Viewed 169 times
2 Answers
1
You can use itertools.zip_longest to zip the lists with different length then use a list comprehension :
>>> from itertools import zip_longest
>>> [i for i,j in izip_longest(a,b) if i!=j]
[1, 2, 4]
Demo:
>>> list(izip_longest(a,b))
[(1, 1), (2, 2), (1, 4), (2, None), (4, None)]
Mazdak
- 105,000
- 18
- 159
- 188
-
i get the following error - ImportError: cannot import name 'izip_longest' – hmm Apr 01 '15 at 10:48
-
@hmm sorry as you are in python 3 you need `zip_longest` fised! – Mazdak Apr 01 '15 at 10:53
0
a = [1,2,1,2,4]
b = [1,2,4]
c= set(a) & set(b)
d=list(c)
The answer is just a little modification to this topic's answer: Find non-common elements in lists
and since you cannot iterate a set object: https://www.daniweb.com/software-development/python/threads/462906/typeerror-set-object-does-not-support-indexing
-
You could do `set(a) - set(b)`, but this will also remove all the duplicates and scramble up the order, which might not be intended. – tobias_k Apr 01 '15 at 11:35