Python replace string pattern with output of function

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臣服心动 2020-11-27 18:24

I have a string in Python, say The quick @red fox jumps over the @lame brown dog.

I\'m trying to replace each of the words that begin with @

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  • 2020-11-27 18:42

    Try:

    import re
    
    match = re.compile(r"@\w+")
    items = re.findall(match, string)
    for item in items:
        string = string.replace(item, my_replace(item)
    

    This will allow you to replace anything that starts with @ with whatever the output of your function is. I wasn't very clear if you need help with the function as well. Let me know if that's the case

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  • 2020-11-27 18:47

    You can pass a function to re.sub. The function will receive a match object as the argument, use .group() to extract the match as a string.

    >>> def my_replace(match):
    ...     match = match.group()
    ...     return match + str(match.index('e'))
    ...
    >>> string = "The quick @red fox jumps over the @lame brown dog."
    >>> re.sub(r'@\w+', my_replace, string)
    'The quick @red2 fox jumps over the @lame4 brown dog.'
    
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  • 2020-11-27 18:48

    A short one with regex and reduce:

    >>> import re
    >>> pat = r'@\w+'
    >>> reduce(lambda s, m: s.replace(m, m + str(m.index('e'))), re.findall(pat, string), string)
    'The quick @red2 fox jumps over the @lame4 brown dog.'
    
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  • 2020-11-27 18:50

    I wasn't aware you could pass a function to a re.sub() either. Riffing on @Janne Karila's answer to solve a problem I had, the approach works for multiple capture groups, too.

    import re
    
    def my_replace(match):
        match1 = match.group(1)
        match2 = match.group(2)
        match2 = match2.replace('@', '')
        return u"{0:0.{1}f}".format(float(match1), int(match2))
    
    string = 'The first number is 14.2@1, and the second number is 50.6@4.'
    result = re.sub(r'([0-9]+.[0-9]+)(@[0-9]+)', my_replace, string)
    
    print(result)
    

    Output:

    The first number is 14.2, and the second number is 50.6000.

    This simple example requires all capture groups be present (no optional groups).

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