Python Style Question

Martin Kemp martin.kemp at ingg.com
Wed Oct 29 13:42:56 CET 2014


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On 29/10/2014 12:01, Rafael Romero Carmona wrote:
> 2014-10-29 12:25 GMT+01:00 Martin Kemp <martin.kemp at ingg.com>: On
> 29/10/2014 10:45, Anton wrote:
>>>> Let's say I have an incoming list of values *l*. Every
>>>> element of *l* can be one of the following options: 1) an
>>>> integer value 2) a string in form of '<int_value>', e.g. '7'
>>>> 3) a string with a json serialization of an integer value,
>>>> e.g. '"7"' 4) something else that should be ignored
>>>> 
>>>> I need to transform this list into another list with values
>>>> from options 1)-3) coerced to int. The code below should do
>>>> this.
>>>> 
>>>> 
>>>> Variant 1 ===
>>>> 
>>>> values = [] for c in l: # Case 1) or 2) try: c_int = int(c)
>>>> except ValueError: pass else: values.add(c_int) continue
>>>> 
>>>> # Case 3) try: c_int = int(json.loads(c)) except ValueError:
>>>> pass else: values.add(c_int) continue
>>>> 
>>>> ===
>>>> 
>>>> Is this code ugly? Does it follow EAFP? Am I missing
>>>> something in language best practice?
>>>> 
>>>> Or maybe below is more preferable way with a nested
>>>> try...except clause?
>>>> 
>>>> Variant 2 === values = [] for c in l: # Case 1) or 2) try:
>>>> c_int = int(c) except ValueError:  # Case 3) try: c_int = 
>>>> int(json.loads(c)) except ValueError: pass else:
>>>> values.add(c_int) continue  else: values.add(c_int) continue
>>>> ===
>>>> 
>>>> Thanks, Anton.
>>>> 
>>>> 
> 
> Your first example is perfectly fine and is EAFP
> 
> 
>> Actually it doesn't work because there is no add function and it 
>> doesn't catch the TypeError function to ignore other exceptions
>> than ValueError. Doesn't it? I tested in Python 2.7.6 and 3.4.
> 
> Personally, I prefer to avoid nesting when it's not necessary.
> 
>> -- https://mail.python.org/mailman/listinfo/python-list

Ah ok, style-wise it was fine.

- -- 
Martin Kemp (martin.kemp at ingg.com)

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