CODEWITHSUNDEEP
pythonlistremove-if
Zac
Zac

Reputation: 372

how to remove characters from items in a list, using another list as reference

I am trying to remove specific characters from items in a list, using another list as a reference. Currently I have:

forbiddenList = ["a", "i"]
tempList = ["this", "is", "a", "test"]
sentenceList = [s.replace(items.forbiddenList, '') for s in tempList]
print(sentenceList)

which I hoped would print:

["ths", "s", "test"]

of course, the forbidden list is quite small and I could replace each individually, but I would like to know how to do this "properly" for when I have an extensive list of "forbidden" items.

Upvotes: 0

Views: 108

Answers (2)

Shashank
Shashank

Reputation: 13869

>>> templist = ['this', 'is', 'a', 'test']
>>> forbiddenlist = ['a', 'i']
>>> trans = str.maketrans('', '', ''.join(forbiddenlist))
>>> [w for w in (w.translate(trans) for w in templist) if w]
['ths', 's', 'test']

This is a Python 3 solution using str.translate and str.maketrans. It should be fast.

You can also do this in Python 2, but the interface for str.translate is slightly different:

>>> templist = ['this', 'is', 'a', 'test']
>>> forbiddenlist = ['a', 'i']
>>> [w for w in (w.translate(None, ''.join(forbiddenlist)) 
...         for w in templist) if w]
['ths', 's', 'test']

Upvotes: 1

Cory Kramer
Cory Kramer

Reputation: 117941

You could use a nested list comprehension.

>>> [''.join(j for j in i if j not in forbiddenList) for i in tempList]
['ths', 's', '', 'test']

It seems like you also want to remove elements if they become empty (as in, all of their characters were in forbiddenList)? If so, you can wrap the whole thing in even another list comp (at the expense of readability)

>>> [s for s in [''.join(j for j in i if j not in forbiddenList) for i in tempList] if s]
['ths', 's', 'test']

Upvotes: 3

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