Data Type API¶
The standard array can have 24 different data types (and has some support for adding your own types). These data types all have an enumerated type, an enumerated type-character, and a corresponding array scalar Python type object (placed in a hierarchy). There are also standard C typedefs to make it easier to manipulate elements of the given data type. For the numeric types, there are also bit-width equivalent C typedefs and named typenumbers that make it easier to select the precision desired.
Warning
The names for the types in c code follows c naming conventions
more closely. The Python names for these types follow Python
conventions. Thus, :cdata:`NPY_FLOAT` picks up a 32-bit float in
C, but numpy.float_
in Python corresponds to a 64-bit
double. The bit-width names can be used in both Python and C for
clarity.
Enumerated Types¶
There is a list of enumerated types defined providing the basic 24 data types plus some useful generic names. Whenever the code requires a type number, one of these enumerated types is requested. The types are all called :cdata:`NPY_{NAME}`:
Some useful aliases of the above types are
Other useful related constants are
The various character codes indicating certain types are also part of
an enumerated list. References to type characters (should they be
needed at all) should always use these enumerations. The form of them
is :cdata:`NPY_{NAME}LTR` where {NAME}
can be
BOOL, BYTE, UBYTE, SHORT, USHORT, INT, UINT, LONG, ULONG, LONGLONG, ULONGLONG, HALF, FLOAT, DOUBLE, LONGDOUBLE, CFLOAT, CDOUBLE, CLONGDOUBLE, DATETIME, TIMEDELTA, OBJECT, STRING, VOID
INTP, UINTP
GENBOOL, SIGNED, UNSIGNED, FLOATING, COMPLEX
The latter group of {NAME}s
corresponds to letters used in the array
interface typestring specification.
Defines¶
Max and min values for integers¶
Number of bits in data types¶
All :cdata:`NPY_SIZEOF_{CTYPE}` constants have corresponding
:cdata:`NPY_BITSOF_{CTYPE}` constants defined. The :cdata:`NPY_BITSOF_{CTYPE}`
constants provide the number of bits in the data type. Specifically,
the available {CTYPE}s
are
BOOL, CHAR, SHORT, INT, LONG, LONGLONG, FLOAT, DOUBLE, LONGDOUBLE
Bit-width references to enumerated typenums¶
All of the numeric data types (integer, floating point, and complex)
have constants that are defined to be a specific enumerated type
number. Exactly which enumerated type a bit-width type refers to is
platform dependent. In particular, the constants available are
:cdata:`PyArray_{NAME}{BITS}` where {NAME}
is INT, UINT,
FLOAT, COMPLEX and {BITS}
can be 8, 16, 32, 64, 80, 96, 128,
160, 192, 256, and 512. Obviously not all bit-widths are available on
all platforms for all the kinds of numeric types. Commonly 8-, 16-,
32-, 64-bit integers; 32-, 64-bit floats; and 64-, 128-bit complex
types are available.
Integer that can hold a pointer¶
The constants NPY_INTP and NPY_UINTP refer to an enumerated integer type that is large enough to hold a pointer on the platform. Index arrays should always be converted to NPY_INTP , because the dimension of the array is of type npy_intp.
C-type names¶
There are standard variable types for each of the numeric data types and the bool data type. Some of these are already available in the C-specification. You can create variables in extension code with these types.
Boolean¶
(Un)Signed Integer¶
Unsigned versions of the integers can be defined by pre-pending a ‘u’ to the front of the integer name.
(Complex) Floating point¶
complex types are structures with .real and .imag members (in that order).
Bit-width names¶
There are also typedefs for signed integers, unsigned integers, floating point, and complex floating point types of specific bit- widths. The available type names are
where {bits}
is the number of bits in the type and can be 8,
16, 32, 64, 128, and 256 for integer types; 16, 32
, 64, 80, 96, 128, and 256 for floating-point types; and 32,
64, 128, 160, 192, and 512 for complex-valued types. Which
bit-widths are available is platform dependent. The bolded bit-widths
are usually available on all platforms.
Printf Formatting¶
For help in printing, the following strings are defined as the correct format specifier in printf and related commands.