string.split bug?

[MetalOne]

string.split("" ) ==> []
string.split("" ,",") ==> ['']

I did not expect these to have different outputs.

I have a string with comma delimited numbers.
There can be zero or more numbers in the string
s = "0x41, 0x42"

I wanted to do
numbers = map(lambda x: int(x,16), string.split(s, ","))

However, when there are no numbers, this generates an error.

[Peter Otten]

Re: string.split bug?

MetalOne wrote:
[color=blue]
> string.split("" ) ==> []
> string.split("" ,",") ==> ['']
>
> I did not expect these to have different outputs.
>
> I have a string with comma delimited numbers.
> There can be zero or more numbers in the string
> s = "0x41, 0x42"
>
> I wanted to do
> numbers = map(lambda x: int(x,16), string.split(s, ","))
>
> However, when there are no numbers, this generates an error.[/color]

It's not a bug, it's a feature. The same question was asked on python-dev
recently, and it turned out that str.split() and str.split(separ ator) are
intended to work differently.

A slightly modernized variant of your example could then be:
[color=blue][color=green][color=darkred]
>>> def numbers(s, sep=None):[/color][/color][/color]
.... return [int(x, 16) for x in s.split(sep) if x]
....[color=blue][color=green][color=darkred]
>>> numbers("aa bb cc\n")[/color][/color][/color]
[170, 187, 204][color=blue][color=green][color=darkred]
>>> numbers("aa,bb, cc", ",")[/color][/color][/color]
[170, 187, 204][color=blue][color=green][color=darkred]
>>> numbers("", ",")[/color][/color][/color]
[]

Peter

[Erik Max Francis]

Re: string.split bug?

MetalOne wrote:
[color=blue]
> string.split("" ) ==> []
> string.split("" ,",") ==> ['']
>
> I did not expect these to have different outputs.[/color]

S.split(None) is a special case which keys off of all whitespace, not
just a single delimiter string. So when presented with an input string
that contains nothing but whitespace, it strips everything and doesn't
find any tokens at all.

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