Replace all non-alphanumeric characters in a string
Question:
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?
Answers:
Regex to the rescue!
import re
s = re.sub('[^0-9a-zA-Z]+', '*', s)
Example:
>>> re.sub('[^0-9a-zA-Z]+', '*', 'h^&ell`.,|o w]{+orld')
'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.
Try:
s = filter(str.isalnum, s)
in Python3:
s = ''.join(filter(str.isalnum, s))
Edit:
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, https://docs.python.org/2/library/re.html
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.
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)
Example:
>>> re.sub('[^0-9a-zA-Z]+', '*', 'h^&ell`.,|o w]{+orld')
'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.
Try:
s = filter(str.isalnum, s)
in Python3:
s = ''.join(filter(str.isalnum, s))
Edit:
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, https://docs.python.org/2/library/re.html
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.