what is this kind of string: b'string' ?

[Stefan Behnel]

Martin v. Loewis, 04.09.2010 18:52:
> Am 01.09.2010 23:32, schrieb Stef Mientki:
>>   in winpdb I see strings like this:
>>
>> >>> a = b'string'
>> >>> a
>> 'string'
>> >>> type(a)
>> <type 'str'>
>>
>> what's the "b" doing in front of the string ?
>
> It's redundant.

Not completely. (I know that you know this, but to those who don't, your 
answer may be misleading.)

If you use 2to3 to convert the above to Python 3 code, it will leave the 
'b' in front of the string, so the resulting string literal will be a bytes 
string in Python 3. If you remove it, the string will become a unicode 
literal. Since the code is syntax compatible with Python 3, simply running 
it in a Python 3 interpreter will also show this behaviour.

So it's redundant in Python 2, but it's no longer redundant when you plan 
to migrate the code to Python 3.

Stefan