keep all alphabetic and numeric characters in python

user_8882027 0
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i have a file.txt and i just want to keep all alphabetic and numeric characters without whitespace and save it in a list, is there another way to do it? this is the new code, is faster. what do you think about it?

fin = open(fcompiti, encoding = 'UTF-8')
s = fin.read()
s = s.replace(' ', '').replace('\n','')
python-3.x
4 Answers

I think it would be a little fast:

import re, string

pattern = re.compile('[\W_]+')

with open('file.txt') as f:
    rdstr = f.read()

rdstr = pattern.sub('', rdstr)

print(rdstr)

For this txt file:

abc342][][]asde34=)$(s)

it will return

abc342asde34s

You can watch it in live here https://repl.it/Ni04/0

user_71280340

You can try with a regex, which may or may not be faster than your approach (depending on the size and structure of your text).

import re

with open('file.txt') as f:
    s = f.read()

s = ''.join(re.findall(r'[\dA-z]+', s))

As a side note, your code is not as memory efficient as it could be. Instead of creating a list in memory and then passing it to join you can use a generator.

s = ''.join(c for c in s if c.isalpha() or c.isnumeric())
# note absence of square brackets
user_14538220

Regex (regular expressions) are your friend.

fin = open('file.txt')
s = fin.read()
alphanums = re.sub(r'[\W_]+', '', s)

This answer will give you more knowledge and examples on how and why this works.

user_69459530

outside of using RegEx, you could also use the .isalnum() builtin function instead of checking .isalpha() and .isnumeric()

with open('file.txt') as fin:
    s = fin.read()
    s = ''.join(c for c in s if c.isalnum())

EDIT: as another user mentioned, you can remove the part that is creating a list of the characters in the file before joining them. the [, ] brackets inside of the .join() aren't necessary.

user_31260850
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