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I have string which is as below (aim is to get rid of non alphanum chars BETWEEN alpha num chars except at end of string)

string: This$#is% Matrix# %!

what i want: This is Matrix# %!

so I want to get rid of non alpha num only between, not at the end.

I tried this regex code, str1 = re.sub(r'([^\s\w]|_)+', ' ', str1) but it gets rid of all non-alp including one at the end.

How do i solve this tricky problem

You can use a negative lookahead assertion.

>>> s = "This$#is% Matrix#  %!"
>>> re.sub(r'([^\s\w]|_)+(?![^\w]*$)', ' ', s)
'This is  Matrix#  %!'

Regex matching non-alphanumeric characters, Regex matching non-alphanumeric characters · python regex. I'm using Python to parse some strings in a list. Some of the strings may only  And we just want to extract the non-alphanumeric characters. This is characters that are neither a number nor an alphabetical character. We can do this in Python with a basic regular expression. We simply write a regular expression that only allows non-alphanumeric characters to be returned. Any other characters will not be returned.

I'd suggest you make two passes:

  1. Replace a bunch of "bad" characters with a space.

  2. Replace a bunch of spaces with a single space.

You have said you want to only remove bad character when there are alphanumerics following. You can use a zero-width lookahead for that:

bad_chars = r'([^\s\w]|_)+(?=\s*\w)'

The (?=...) is a positive lookahead, and it looks ahead to see if the pattern \s*\w is matched from the current position, but does not move forward- it just looks.

Then replace with spaces, collapse the spaces, and you're done:

re.sub(bad_chars, ' ', mystring)
re.sub('\s\s+', ' ', mystring)

How to Extract Only Non-Alphanumeric Characters from a String in , In this article, we show how to extract non-alphanumeric characters from a string in Python using regular expressions. Replace non alphanumeric characters except some exceptions python. Tag: python,regex,alphanumeric

Hi I feel my question still hasnt been answered,as you can see in the output below, I only want the non alpha num between the 2 alpha chars to be replace by 1 space, the part after matrix, should be untouched as its not between alphanum chars.

Inout string This$#is% Matrix#(2 space here) %!

Your Output (stdout) This is Matrix#(1 space here) %!

Expected OutputDownload This is Matrix#(2 space here)%!

How to replace all non-alphanumeric characters in a string in Python, sub(pattern, repl, string) with pattern as "[^0-9a-zA-Z]+" to replace every non-​alphanumeric character with repl in string . a_string = "a*c!" new_string = re  Python has a special sequence \w for matching alphanumeric and underscore when the LOCALE and UNICODE flags are not specified. So you can modify your pattern as, So you can modify your pattern as, pattern = '^\w+$'

Regular Expression HOWTO, Matches any non-alphanumeric character; this is equivalent to the class [^a-zA-​Z0-9_]. These sequences can be included inside a character class  What is the best way to strip all non alphanumeric characters from a string, using Python? The solutions presented in the PHP variant of this question will probably work with some minor adjustments, but don't seem very 'pythonic' to me.

Search, which should be either a string of alphanumeric characters (for protocol 0) [#]_ or only needs to be used if the key contains spaces or non-alphanumeric characters. If the regex pattern is expressed in bytes, this is equivalent to the class  A RegEx, or Regular Expression, is a sequence of characters that forms a search pattern. RegEx can be used to check if a string contains the specified search pattern. RegEx Module

7.2. re — Regular expression operations, Regular expressions use the backslash character ( '\' ) to indicate matches any non-alphanumeric character; this is equivalent to the set  Regular expressions (called REs, or regexes, or regex patterns) are essentially a tiny, highly specialized programming language embedded inside Python and made available through the re module. Using this little language, you specify the rules for the set of possible strings that you want to match; this set might contain English sentences, or e-mail addresses, or TeX commands, or anything you like.

  • find the index of the last alphanumeric character, i and apply regex from index 0 to i.