Python keep only alphanumeric words from list

Question

I have a list of words resembling the following

    mylist=["hi", "h_ello", "how're", "you", "@list"]

I would like to pull out all of the non-alpha numeric characters to give a results such as:

                  "h_ello", "how're", "@list"

Please note I have a much longer list in real life, and it contains some non-alpha numeric instances such as ~, ?, >, =, + etc.

Does anyone know how to do this ,please? Thank you

Answer 1

Use str.isalpha()

Ex:

mylist=["hi", "h_ello", "how're", "you", "@list"]
print([i for i in mylist if not i.isalpha()])

Output:

['h_ello', "how're", '@list']

Answer 2

You can use a list comprehension in combination with isalnum() function.

mylist=["hi", "h_ello", "how're", "you", "@list"]
print([i for i in mylist if not i.isalnum()])

Output

['h_ello', "how're", '@list']

From python documentation :

str.isalnum() Return true if all characters in the string are alphanumeric and there is at least one character, false otherwise. A character c is alphanumeric if one the following returns True: c.isalpha() , c.isdecimal() , c.isdigit() , or c.isnumeric() .

Answer 3

You can also use filter with re :

import re
mylist=["hi", "h_ello", "how're", "you", "@list"]
new_list = list(filter(lambda x:re.findall('[\W_]', x), mylist))

Output:

['h_ello', "how're", '@list']

Answer 4

Better you go for isalnum or regex , Here i tried a little different approach just for fun, This is not for production code it will take time, I just tried to show you a different way :

import unicodedata
import sys

mylist = ["hi", "h_ello", "how're", "you", "@list"]


def translate(text_):
    pun=[i for i in range(sys.maxunicode) if unicodedata.category(chr(i)).startswith('P')]

    if True in [True if ord(i) in pun else False for i in text_ ]:
        return text_


print(list(filter(lambda x:x,[translate(i) for i in mylist])))

output:

['h_ello', "how're", '@list']