Replace all non-alphanumeric characters in a string

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I have a string with which i want to replace any character that isn’t a standard character or number such as (a-z or 0-9) with an asterisk. For example, “h^&ell`.,|o w]{+orld” is replaced with “h*ell*o*w*orld”. Note that multiple characters such as “^&” get replaced with one asterisk. How would I go about doing this?

Regex to the rescue!

import re

s = re.sub('[^0-9a-zA-Z]+', '*', s)


>>> re.sub('[^0-9a-zA-Z]+', '*', 'h^&ell`.,|o w]{+orld')

The pythonic way.

print "".join([ c if c.isalnum() else "*" for c in s ])

This doesn’t deal with grouping multiple consecutive non-matching characters though, i.e.

"h^&i => "h**i not "h*i" as in the regex solutions.


s = filter(str.isalnum, s)

in Python3:

s="".join(filter(str.isalnum, s))

realized that the OP wants to replace non-chars with ‘*’. My answer does not fit

Use \W which is equivalent to [^a-zA-Z0-9_]. Check the documentation,

import re
s="h^&ell`.,|o w]{+orld"
replaced_string = re.sub(r'\W+', '*', s)
output: 'h*ell*o*w*orld'

update: This solution will exclude underscore as well. If you want only alphabets and numbers to be excluded, then solution by nneonneo is more appropriate.

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