[Numpy-discussion] Data types in Numerical Python
Here is an example that works for any working numpy installation: import numpy as npy npy.zeros((256, 256)) This suggestion from David did work so far, and removing the other import line enabled the program to run. However, the data types the program used as defaults for variables has changed, and now I am getting error messages about data types. It seems that some variables are getting a default designation as floats. Before I installed numpy and needed 2-D arrays, the program was working with the default types, and I did not have to specify types. Is there a clear tutorial that describes a means to assign data types for each variable as in C, so that I don't obtain error messages about data types? Because I am simulating code for a DSP processor, the data types I need are unsigned bytes, unsigned 32-bit ints, and signed 32-bit ints. In some cases I can use unsigned and signed 16-bit ints. Also, what data types are valid for use with local operations such as exclusive or? ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] Data types in Numerical Python
2008/10/12 Linda Seltzer [EMAIL PROTECTED]: Here is an example that works for any working numpy installation: import numpy as npy npy.zeros((256, 256)) This suggestion from David did work so far, and removing the other import line enabled the program to run. However, the data types the program used as defaults for variables has changed, and now I am getting error messages about data types. It seems that some variables are getting a default designation as floats. Before I installed numpy and needed 2-D arrays, the program was working with the default types, and I did not have to specify types. Is there a clear tutorial that describes a means to assign data types for each variable as in C, so that I don't obtain error messages about data types? Python is a dynamically-typed language (unlike C), so variables do not have type. That is, a variable can refer to an object of any type; if you need to know what type of object a variable currently refers to you must inspect the object. You may want to go through one of the brief introduction-to-python tutorials that are on the python website just to get comfortable with the language. (For example, understanding the meaning and syntax of import statements.) When you create a numpy array, you can specify its type. You can also explicitly or implicitly convert the types of numpy arrays. I recommend you select a data type, let's say np.uint32, and make sure various arrays are created containing that type: np.zeros((m,n),dtype=np.uint32) np.arange(10,dtype=np.uint32) x.astype(np.uint32) np.array([1,2,3,4.5], dtype=np.uint32) et cetera. Most operations (addition, multiplication, maximum) will preserve the data type of arrays they are given (but if you supply two different data types numpy will attempt to choose the larger). Because I am simulating code for a DSP processor, the data types I need are unsigned bytes, unsigned 32-bit ints, and signed 32-bit ints. In some cases I can use unsigned and signed 16-bit ints. Also, what data types are valid for use with local operations such as exclusive or? The numpy data types you want are described by dtype objects. These can in principle become quite complicated, but the ones you need are given names already: np.uint8 np.uint32 np.int32 np.uint16 np.int16 You can specify any of these as dtype= arguments to the various numpy functions. If you need really rigid typing, python may not be the ideal language for you. Good luck, Anne ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] Data types in Numerical Python
Linda Seltzer wrote: Here is an example that works for any working numpy installation: import numpy as npy npy.zeros((256, 256)) This suggestion from David did work so far, and removing the other import line enabled the program to run. However, the data types the program used as defaults for variables has changed, and now I am getting error messages about data types. It seems that some variables are getting a default designation as floats. Before I installed numpy and needed 2-D arrays, the program was working with the default types, and I did not have to specify types. Is there a clear tutorial that describes a means to assign data types for each variable as in C, so that I don't obtain error messages about data types? Because I am simulating code for a DSP processor, the data types I need are unsigned bytes, unsigned 32-bit ints, and signed 32-bit ints. In some cases I can use unsigned and signed 16-bit ints. Also, what data types are valid for use with local operations such as exclusive or? ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion You can specify the type in the zeros command import numpy as npy npy.zeros((256, 256), npy.uint32) or you can convert an array between types at any point using the .astype(npy.uint16) notation like this npy.zeros((256,256)).astype(npy.uint16) I am not sure if there are any tutorials on this, but here are the types you are interested in: npy.uint32 npy.uint16 npy.int32 npy.int16 ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] Data types in Numerical Python
On Oct 12, 2008, at 5:26 PM, Anne Archibald wrote: Python is a dynamically-typed language (unlike C), so variables do not have type. Another way to think of it for C people is that all variables have the same type, which is reference to Python object. It's the objects which are typed, and not the variable. Andrew [EMAIL PROTECTED] ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
Re: [Numpy-discussion] Data types in Numerical Python
On Sun, Oct 12, 2008 at 9:11 AM, Linda Seltzer [EMAIL PROTECTED]wrote: Here is an example that works for any working numpy installation: import numpy as npy npy.zeros((256, 256)) This suggestion from David did work so far, and removing the other import line enabled the program to run. However, the data types the program used as defaults for variables has changed, and now I am getting error messages about data types. It seems that some variables are getting a default designation as floats. Before I installed numpy and needed 2-D arrays, the program was working with the default types, and I did not have to specify types. Yes, the default type of the functions zeros and ones have changed from integer to float. If your program is short you could send it as an attachment so we could look at it. Chuck ___ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
