On Friday 18 August 2006 16:51, Travis Oliphant wrote: > Sebastian Haase wrote: > > On Friday 18 August 2006 15:25, Travis Oliphant wrote: > >> Sebastian Haase wrote: > >>> On Friday 18 August 2006 11:38, Travis Oliphant wrote: > >>>> Sebastian Haase wrote: > >>>>> Hi, > >>>>> array dtype descriptors have an attribute itemsize that gives the > >>>>> total number of bytes required for an item of that dtype. > >>>>> > >>>>> Scalar types, like numy.int32, also have that attribute, > >>>>> but it returns "something else" - don't know what: > >>>>> > >>>>> > >>>>> Furthermore there are *lot's* of more attributes to a scalar dtype, > >>>>> e.g. > >>>> > >>>> The scalar types are actual Python types (classes) whereas the dtype > >>>> objects are instances. > >>>> > >>>> The attributes you are seeing of the typeobject are very useful when > >>>> you have an instance of that type. > >>>> > >>>> With numpy.int32.itemsize you are doing the equivalent of > >>>> numpy.dtype.itemsize > >>> > >>> but why then do I not get the result 4 ? > >> > >> Because it's not a "class" attribute, it's an instance attribute. > >> > >> What does numpy.dtype.itemsize give you? > > > > I'm really sorry for being so dumb - but HOW can I get then the number of > > bytes needed by a given scalar type ? > > Ah, the real question. Sorry for not catching it earlier. I've been in > "make sure this isn't a bug mode" for a long time. > > If you have a scalar type you could create one and then check the itemsize: > > int32(0).itemsize > > Or you could look at the name and parse out how big it is. > > There is also a stored dictionary-like object that returns the number of > bytes for any data-type recognized: > > numpy.nbytes[int32]
Thanks, that seems to be a handy "dictionary-like object" Just for the record - in the meantime I found this: >>> N.dtype(N.int32).itemsize 4 Cheers, Sebastian ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Numpy-discussion mailing list Numpy-discussion@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/numpy-discussion
