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 typecharacter, 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 bitwidth 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, NPY_FLOAT
picks up a 32bit float in
C, but numpy.float_
in Python corresponds to a 64bit
double. The bitwidth 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 NPY_{NAME}
:

NPY_BOOL
¶ The enumeration value for the boolean type, stored as one byte. It may only be set to the values 0 and 1.

NPY_BYTE
¶

NPY_INT8
¶ The enumeration value for an 8bit/1byte signed integer.

NPY_SHORT
¶

NPY_INT16
¶ The enumeration value for a 16bit/2byte signed integer.

NPY_INT
¶

NPY_INT32
¶ The enumeration value for a 32bit/4byte signed integer.

NPY_LONG
¶ Equivalent to either NPY_INT or NPY_LONGLONG, depending on the platform.

NPY_LONGLONG
¶

NPY_INT64
¶ The enumeration value for a 64bit/8byte signed integer.

NPY_UBYTE
¶

NPY_UINT8
¶ The enumeration value for an 8bit/1byte unsigned integer.

NPY_USHORT
¶

NPY_UINT16
¶ The enumeration value for a 16bit/2byte unsigned integer.

NPY_UINT
¶

NPY_UINT32
¶ The enumeration value for a 32bit/4byte unsigned integer.

NPY_ULONG
¶ Equivalent to either NPY_UINT or NPY_ULONGLONG, depending on the platform.

NPY_ULONGLONG
¶

NPY_UINT64
¶ The enumeration value for a 64bit/8byte unsigned integer.

NPY_HALF
¶

NPY_FLOAT16
¶ The enumeration value for a 16bit/2byte IEEE 7542008 compatible floating point type.

NPY_FLOAT
¶

NPY_FLOAT32
¶ The enumeration value for a 32bit/4byte IEEE 754 compatible floating point type.

NPY_DOUBLE
¶

NPY_FLOAT64
¶ The enumeration value for a 64bit/8byte IEEE 754 compatible floating point type.

NPY_LONGDOUBLE
¶ The enumeration value for a platformspecific floating point type which is at least as large as NPY_DOUBLE, but larger on many platforms.

NPY_CFLOAT
¶

NPY_COMPLEX64
¶ The enumeration value for a 64bit/8byte complex type made up of two NPY_FLOAT values.

NPY_CDOUBLE
¶

NPY_COMPLEX128
¶ The enumeration value for a 128bit/16byte complex type made up of two NPY_DOUBLE values.

NPY_CLONGDOUBLE
¶ The enumeration value for a platformspecific complex floating point type which is made up of two NPY_LONGDOUBLE values.

NPY_DATETIME
¶ The enumeration value for a data type which holds dates or datetimes with a precision based on selectable date or time units.

NPY_TIMEDELTA
¶ The enumeration value for a data type which holds lengths of times in integers of selectable date or time units.

NPY_STRING
¶ The enumeration value for ASCII strings of a selectable size. The strings have a fixed maximum size within a given array.

NPY_UNICODE
¶ The enumeration value for UCS4 strings of a selectable size. The strings have a fixed maximum size within a given array.

NPY_OBJECT
¶ The enumeration value for references to arbitrary Python objects.

NPY_VOID
¶ Primarily used to hold struct dtypes, but can contain arbitrary binary data.
Some useful aliases of the above types are

NPY_INTP
¶ The enumeration value for a signed integer type which is the same size as a (void *) pointer. This is the type used by all arrays of indices.

NPY_UINTP
¶ The enumeration value for an unsigned integer type which is the same size as a (void *) pointer.

NPY_MASK
¶ The enumeration value of the type used for masks, such as with the
NPY_ITER_ARRAYMASK
iterator flag. This is equivalent toNPY_UINT8
.

NPY_DEFAULT_TYPE
¶ The default type to use when no dtype is explicitly specified, for example when calling np.zero(shape). This is equivalent to
NPY_DOUBLE
.
Other useful related constants are

NPY_NTYPES
¶ The total number of builtin NumPy types. The enumeration covers the range from 0 to NPY_NTYPES1.

NPY_NOTYPE
¶ A signal value guaranteed not to be a valid type enumeration number.

NPY_USERDEF
¶ The start of type numbers used for Custom Data types.
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 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¶

NPY_MAX_INT{bits}

NPY_MAX_UINT{bits}

NPY_MIN_INT{bits}
These are defined for
{bits}
= 8, 16, 32, 64, 128, and 256 and provide the maximum (minimum) value of the corresponding (unsigned) integer type. Note: the actual integer type may not be available on all platforms (i.e. 128bit and 256bit integers are rare).

NPY_MIN_{type}
This is defined for
{type}
= BYTE, SHORT, INT, LONG, LONGLONG, INTP

NPY_MAX_{type}
This is defined for all defined for
{type}
= BYTE, UBYTE, SHORT, USHORT, INT, UINT, LONG, ULONG, LONGLONG, ULONGLONG, INTP, UINTP
Number of bits in data types¶
All NPY_SIZEOF_{CTYPE}
constants have corresponding
NPY_BITSOF_{CTYPE}
constants defined. The 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
Bitwidth 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 bitwidth type refers to is
platform dependent. In particular, the constants available are
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 bitwidths are available on
all platforms for all the kinds of numeric types. Commonly 8, 16,
32, 64bit integers; 32, 64bit floats; and 64, 128bit 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.
Ctype 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 Cspecification. You can create variables in extension code with these types.
(Un)Signed Integer¶
Unsigned versions of the integers can be defined by prepending a ‘u’ to the front of the integer name.

npy_(u)byte
(unsigned) char

npy_(u)short
(unsigned) short

npy_(u)int
(unsigned) int

npy_(u)long
(unsigned) long int

npy_(u)longlong
(unsigned long long int)

npy_(u)intp
(unsigned) Py_intptr_t (an integer that is the size of a pointer on the platform).
(Complex) Floating point¶

npy_(c)float
float

npy_(c)double
double

npy_(c)longdouble
long double
complex types are structures with .real and .imag members (in that order).
Bitwidth 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
npy_int{bits}
,npy_uint{bits}
,npy_float{bits}
, andnpy_complex{bits}
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 floatingpoint types; and 32,
64, 128, 160, 192, and 512 for complexvalued types. Which
bitwidths are available is platform dependent. The bolded bitwidths
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.
NPY_LONGLONG_FMT
,NPY_ULONGLONG_FMT
,NPY_INTP_FMT
,NPY_UINTP_FMT
,NPY_LONGDOUBLE_FMT