On Sat, Aug 15, 2009 at 4:06 PM, MRAB <pyt...@mrabarnett.plus.com> wrote:
> ryles wrote:
>
>> On Aug 14, 8:22 pm, candide <cand...@free.invalid> wrote:
>>
>>> Suppose you need to split a string into substrings of a given size
>>> (except
>>> possibly the last substring). I make the hypothesis the first slice is at
>>> the
>>> end of the string.
>>> A typical example is provided by formatting a decimal string with
>>> thousands
>>> separator.
>>>
>>> What is the pythonic way to do this ?
>>>
>>> For my part, i reach to this rather complicated code:
>>>
>>> # ----------------------
>>>
>>> def comaSep(z,k=3, sep=','):
>>> z=z[::-1]
>>> x=[z[k*i:k*(i+1)][::-1] for i in range(1+(len(z)-1)/k)][::-1]
>>> return sep.join(x)
>>>
>>> # Test
>>> for z in ["75096042068045", "509", "12024", "7", "2009"]:
>>> print z+" --> ", comaSep(z)
>>>
>>> # ----------------------
>>>
>>> outputting :
>>>
>>> 75096042068045 --> 75,096,042,068,045
>>> 509 --> 509
>>> 12024 --> 12,024
>>> 7 --> 7
>>> 2009 --> 2,009
>>>
>>> Thanks
>>>
>>
>> py> s='1234567'
>> py> ','.join(_[::-1] for _ in re.findall('.{1,3}',s[::-1])[::-1])
>> '1,234,567'
>> py> # j/k ;)
>>
>
> If you're going to use re, then:
>
> >>> for z in ["75096042068045", "509", "12024", "7", "2009"]:
> print re.sub(r"(?<=.)(?=(?:...)+$)", ",", z)
>
>
> 75,096,042,068,045
> 509
> 12,024
> 7
> 2,009
>
Can you please break down this regex?
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