[Numpy-discussion] dtype for a single char

sam tygier samtygier@yahoo.co...
Thu Mar 4 02:34:06 CST 2010


Robert Kern wrote:
> On Wed, Mar 3, 2010 at 15:14, sam tygier <samtygier@yahoo.co.uk> wrote:
>> Hello
>>
>> today i was caught out by trying to use 'a' as a dtype for a single character. a simple example would be:
>>
>>>>> array([('a',1),('b',2),('c',3)], dtype=[("letter", "a"), ("number", "i")])
>> array([('', 1), ('', 2), ('', 3)],
>>      dtype=[('letter', '|S0'), ('number', '<i4')])
>>
>> the fix seems to be using 'a1' instead
>>
>>>>> array([('a',1),('b',2),('c',3)], dtype=[("letter", "a1"), ("number", "i")])
>> array([('a', 1), ('b', 2), ('c', 3)],
>>      dtype=[('letter', '|S1'), ('number', '<i4')])
>>
>> this seems odd to me, as other types eg 'i' and 'f' can be used on their own. is there a reason for this?
> 
> Other types have a sensible default determined by the platform.
> 

I don't understand. char has sensible default size on my platform (and all the others i am familiar with), 1 byte.

Sam



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