python re.sub with a list of words to find
list, python, regex
Solution
The plus symbol is an operator in regex meaning 'one or more repetitions of the preceding'. E.g., `x+` means one or more repetitions of `x`. If you want to find and replace actual `+` signs, you need to escape it like this: `re.sub('\+', '', string)`. So change the first entry in your exclusionList.
You can also eliminate the for loop, like this:
exclusions = '|'.join(exclusionList)
first_word = re.sub(exclusions, '', first_word)
The pipe symbol `|` indicates a disjunction in regex, so `x|y|z` matches x or y or z.
Problem
I am not too familiar with RE but I am trying to iterate over a list and use `re.sub` to take out multiple items from a large block of text that is held in the variable `first_word`. I use `re.sub` to remove tags first and this works fine, but I next want to remove all the strings in the `exclusionList` variable and I am not sure how to do this. Thanks for the help, here is the code that raises the exception. ``` exclusionList = ['+','of','<ET>f.','to','the','<L>L.</L>'] for a in range(0, len(exclusionList)): first_word = re.sub(exclusionList[a], '',first_word) ``` And the exception : ``` first_word = re.sub(exclusionList[a], '',first_word) File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/re.py", line 151, in sub return _compile(pattern, flags).sub(repl, string, count) File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/re.py", line 245, in _compile raise error, v # invalid expression error: nothing to repeat ```