String/Number Conversion

Andreas Hofmann asdfasdfasdfasdfasdf at arcor.de
Sun Sep 7 00:00:07 CEST 2008


Thanks a lot, I got it working now.
Thanks also to the other guys, your numerous hints were really valuable!

Kind regards,
Andy

John Machin schrieb:
> On Sep 7, 7:04 am, Andreas Hofmann <asdfasdfasdfasdfa... at arcor.de>
> wrote:
>> Hello Folks!
>>
>> I've got a little problem here, which which really creeps me out at the
>> moment.
>> I've got some strings, which only contain numbers plus eventually one
>> character as si-postfix (k for kilo, m for mega, g for giga). I'm trying
>> to convert those strings to integers, with this function:
>>
>> def eliminate_postfix(value):
>>          if type(value) is str:
> 
> Don't use "is" unless you are really sure that "==" won't do the job.
> Better idiom:
> if isinstance(value, str):
> 
>>                  value.upper()
> 
> This causes your "mult is always 1" problem. You need:
>     value = value.upper()
> Why? Because strings are immutable. String methods like upper return a
> new string, they don't change the existing string.
> 
>>                  if value.endswith('K'):
>>                          mult = 1000
>>                  elif value.endswith('M'):
>>                          mult = 1000000
>>                  elif value.endswith('G'):
>>                          mult = 1000000000
>>                  else:
>>                          mult = 1
>>
>>                  if mult is 1:
> 
> Lose "is". In fact, lose the whole "if" statement. See below.
> 
>>                          value = string.atoi(value)
> 
> Don't use deprecated functions from the string module. Use the built-
> in float function to convert from text.
> 
>>                  else:
>>                          value = string.atoi(value[:-1]) * mult
>>          return value
> 
> Those last few statements look somewhat tortuous. Try this:
>     else: # mult would be 1, but we don't need it
>         return float(value)
>     return float(value[:-1]) * mult
> 
> HTH,
> John



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