![]() ![]() Note as I have already pointed out that the negative lookahead ?! will not match when wordB is followed by a single whitespace and wordc. I replaced wordc with swordc since that is more explicit. The only difference is that not the regex matches whitespace OR. Preserving your original regex you can use: Hello the problem is not the expression but the HTML out put that are not considered as whitespace. Are you capturing the whitespace to a group for a reason? If not you could just remove the brackets, i.e. (s*) – the brackets indicate a capturing group. You may want to consider if you want at least one space. * will match 0 or more spaces so it will match wordAwordB. Of course, if you do want to match lines with wordc after wordB then you shouldn’t use a negative lookahead. If you want to match against more than one space before wordc you can use (?!s*wordc) for 0 or more spaces or (?!s* wordc) for 1 or more spaces depending on what your intention is. You may want to be more precise and use (?!swordc). Currently you are relying on the space after ?! to match the whitespace. (?! wordc) is a negative lookahead, so you wont match lines wordA wordB wordc which is assume is intended (and is why the last line is not matched). Note that all matches are replaced no matter how many spaces. Here are some example matches and the associated replacement output: Note the single space between ?! and wordc which means that wordA wordB wordc will not match, but wordA wordB wordc will. This means match wordA followed by 0 or more spaces followed by wordB, but do not match if followed by wordc. Assuming that it is doing what you want it to. Of course, you can comment out the individual whitespace Unicode characters you don’t want to match as required by your own application.Your regex should work ‘as-is’. The following code snippet uses the UNICODE_WHITESPACES constant but comments out the newline whitespaces so that newline-related characters such as '\n' and '\r' are not matched anymore! import re Method 3: Match Individual Different Whitespaces Except Newlines ![]() Of course, you can restrict this to only contain whitespaces that are not newline-related. ![]() Here’s a variant that finds all matches of whitespace characters in a given text: import re You can generate a character class using the string expression ''. The following list of Unicode whitespace characters UNICODE_WHITESPACES contains all major whitespace variants you may want to check your string for. If you want more fine-grained control about which whitespace characters to match and which not, you can use the following baseline approach. The previous method only matches the horizontal tab ( U 0009) and breaking space ( U 0020) characters. ? Learn More: Character Class (Character Set) - The Ultimate Guide for Python Method 2: Match Individual Different Whitespace Characters For the given pattern, it matches either the empty space ' ' or the tabular character '\t'. The character class essentially is an OR relationship, i.e., one item within the character class is matched. The reason there’s a space in the pattern is to match the empty space. Here’s an example where you replace all separating whitespace (except newline) with a comma to receive a CSV formatted output: import reĭ,e,f Why the space in the pattern ? If you want to match an arbitrary number of empty spaces except for newlines, append the plus quantifier to the pattern like so: . The character class pattern matches one empty space ' ' or a tabular character '\t', but not a newline character. ? Challenge: How to design a regular expression pattern that matches whitespace characters such as the empty space ' ' and the tabular character '\t', but not the newline character '\n'?Īn example of this would be to replace all whitespaces (except newlines) between a space-delimited file with commas to obtain a CSV. Method 3: Match Individual Different Whitespaces Except Newlines.Method 2: Match Individual Different Whitespace Characters. ![]()
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