不使用正则表达式删除字符串中的标点和空格

Question

I used import string and string.punctuation but I realized I still have '…' after conducting string.split() . I also get '' , which I don't know why I would get it after doing strip( ). As far as I understand, strip() removes the peripheral spaces, so if I have spaces between a string it would not matter:

>>> s = 'a dog    barks    meow!   @  … '
>>> s.strip()
'a dog    barks    meow!   @  …'


>>> import string
>>> k = []
>>> for item in s.split():
...  k.append(item.strip(string.punctuation))
... 
>>> k
['a', 'dog', 'barks', 'meow', '', '…']

I would like to get rid of '', '…' , the final output I'd like is ['a', 'dog', 'barks', 'meow'] .

I would like to refrain from using regex, but if that's the only solution I will consider it .. for now I'm more interested in solving this without resorting to regex.

Answer 1

You can remove punctuation by retaining only alphanumeric characters and spaces:

s = 'a dog    barks    meow!   @  …'
print(''.join(c for c in s if c.isalnum() or c.isspace()).split())

This outputs:

['a', 'dog', 'barks', 'meow']

Answer 2

I used the following:

s = 'a dog    barks    Meow!   @  … '



import string
p = string.punctuation+'…'
k = []
for item in s.split():
    k.append(item.strip(p).lower())


k = [x for x in k if x]

Answer 3

building on the accepted answer to this question :

import itertools

k = []
for ok, grp in itertools.groupby(s, lambda c: c.isalnum()):
    if ok:
        k.append(''.join(list(grp)))

or the same as a one-liner (except for the import):

k = [''.join(list(grp)) for ok, grp in itertools.groupby(s, lambda c: c.isalnum()) if ok]

itertools.groupby() scans the string s as a list of characters, grouping them ( grp ) by the value ( ok ) of the lambda expression. The if ok filters out the groups not matching the lambda. The groups are iterators that have to be converted to a list of characters and then joined to get back the words.

The meaning of isalnum() is essentially “is alphanumeric”. Depending on your use case, you might prefer isalpha() . In both cases, for this input:

s = 'a 狗    barks    meow!   @  …'

the output is

['a', '狗', 'barks', 'meow']

(For experts: this reminds us of the problem that not in all languages words are separated by non-word characters - eg )