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[Python-Dev] Call for prudence about PEP-572

Anthony Flury anthony.flury at btinternet.com
Mon Jul 9 18:26:25 EDT 2018 
On 09/07/18 08:26, Matěj Cepl wrote:
> On 2018-07-07, 15:48 GMT, Guido van Rossum wrote:
>>      if validate(name := re.search(pattern, line).group(1)):
>>          return name
> Except there is no error handling for situations when
> re.search() returns None, so one shouldn't use it anyway (most
> of the time). Which seems to me like another nice example why
> one should stay away from this style as much as possible. I am
> too lazy to be tempted into this
> nice-example-terrible-production-code world.
So wrap it in a try/except to capture the re.search returning None:

     try:
         if validate(name := re.search(pattern, line).group(1)):
              return name
except TypeError:
           # No match case

And this solution is even better if the validate function raises an 
exception rather than True/False

which I think is much better than trying to do multiple steps :

    match = re.search(pattern, line)
    if match is not None:
        name = match.group(1)
        if name and validate(name):
               return name
        else:
            # No valid case
    else:
        # No Match case

> Best,
>
> Matěj


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Anthony Flury
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