The standard array can have 24 different data types (and has somesupport for adding your own types). These data types all have anenumerated type, an enumerated type-character, and a correspondingarray scalar Python type object (placed in a hierarchy). There arealso standard C typedefs to make it easier to manipulate elements ofthe given data type. For the numeric types, there are also bit-widthequivalent C typedefs and named typenumbers that make it easier toselect the precision desired.
Warning
The names for the types in c code follows c naming conventionsmore closely. The Python names for these types follow Pythonconventions. Thus,NPY_FLOAT picks up a 32-bit float inC, butnumpy.float_ in Python corresponds to a 64-bitdouble. The bit-width names can be used in both Python and C forclarity.
There is a list of enumerated types defined providing the basic 24data types plus some useful generic names. Whenever the code requiresa type number, one of these enumerated types is requested. The typesare all calledNPY_{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 8-bit/1-byte signed integer.
NPY_SHORT¶NPY_INT16¶The enumeration value for a 16-bit/2-byte signed integer.
NPY_INT¶NPY_INT32¶The enumeration value for a 32-bit/4-byte signed integer.
NPY_LONG¶Equivalent to either NPY_INT or NPY_LONGLONG, depending on theplatform.
NPY_LONGLONG¶NPY_INT64¶The enumeration value for a 64-bit/8-byte signed integer.
NPY_UBYTE¶NPY_UINT8¶The enumeration value for an 8-bit/1-byte unsigned integer.
NPY_USHORT¶NPY_UINT16¶The enumeration value for a 16-bit/2-byte unsigned integer.
NPY_UINT¶NPY_UINT32¶The enumeration value for a 32-bit/4-byte unsigned integer.
NPY_ULONG¶Equivalent to either NPY_UINT or NPY_ULONGLONG, depending on theplatform.
NPY_ULONGLONG¶NPY_UINT64¶The enumeration value for a 64-bit/8-byte unsigned integer.
NPY_HALF¶NPY_FLOAT16¶The enumeration value for a 16-bit/2-byte IEEE 754-2008 compatible floatingpoint type.
NPY_FLOAT¶NPY_FLOAT32¶The enumeration value for a 32-bit/4-byte IEEE 754 compatible floatingpoint type.
NPY_DOUBLE¶NPY_FLOAT64¶The enumeration value for a 64-bit/8-byte IEEE 754 compatible floatingpoint type.
NPY_LONGDOUBLE¶The enumeration value for a platform-specific floating point type which isat least as large as NPY_DOUBLE, but larger on many platforms.
NPY_CFLOAT¶NPY_COMPLEX64¶The enumeration value for a 64-bit/8-byte complex type made up oftwo NPY_FLOAT values.
NPY_CDOUBLE¶NPY_COMPLEX128¶The enumeration value for a 128-bit/16-byte complex type made up oftwo NPY_DOUBLE values.
NPY_CLONGDOUBLE¶The enumeration value for a platform-specific complex floating pointtype which is made up of two NPY_LONGDOUBLE values.
NPY_DATETIME¶The enumeration value for a data type which holds dates or datetimes witha precision based on selectable date or time units.
NPY_TIMEDELTA¶The enumeration value for a data type which holds lengths of times inintegers of selectable date or time units.
NPY_STRING¶The enumeration value for ASCII strings of a selectable size. Thestrings have a fixed maximum size within a given array.
NPY_UNICODE¶The enumeration value for UCS4 strings of a selectable size. Thestrings 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 arbitrarybinary data.
Some useful aliases of the above types are
NPY_INTP¶The enumeration value for a signed integer type which is the samesize as a (void *) pointer. This is the type used by allarrays of indices.
NPY_UINTP¶The enumeration value for an unsigned integer type which is thesame size as a (void *) pointer.
NPY_MASK¶The enumeration value of the type used for masks, such as withtheNPY_ITER_ARRAYMASK iterator flag. This is equivalenttoNPY_UINT8.
NPY_DEFAULT_TYPE¶The default type to use when no dtype is explicitly specified, forexample when calling np.zero(shape). This is equivalent toNPY_DOUBLE.
Other useful related constants are
NPY_NTYPES¶The total number of built-in NumPy types. The enumeration coversthe range from 0 to NPY_NTYPES-1.
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 ofan enumerated list. References to type characters (should they beneeded at all) should always use these enumerations. The form of themisNPY_{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 arrayinterface typestring specification.
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 providethe maximum (minimum) value of the corresponding (unsigned) integertype. Note: the actual integer type may not be available on allplatforms (i.e. 128-bit and 256-bit 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
AllNPY_SIZEOF_{CTYPE} constants have correspondingNPY_BITSOF_{CTYPE} constants defined. TheNPY_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
All of the numeric data types (integer, floating point, and complex)have constants that are defined to be a specific enumerated typenumber. Exactly which enumerated type a bit-width type refers to isplatform dependent. In particular, the constants available arePyArray_{NAME}{BITS} where{NAME} isINT,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 onall platforms for all the kinds of numeric types. Commonly 8-, 16-,32-, 64-bit integers; 32-, 64-bit floats; and 64-, 128-bit complextypes are available.
The constantsNPY_INTP andNPY_UINTP refer to anenumerated integer type that is large enough to hold a pointer on theplatform. Index arrays should always be converted toNPY_INTP, because the dimension of the array is of type npy_intp.
There are standard variable types for each of the numeric data typesand the bool data type. Some of these are already available in theC-specification. You can create variables in extension code with thesetypes.
Unsigned versions of the integers can be defined by pre-pending 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 onthe platform).
npy_(c)floatfloat
npy_(c)doubledouble
npy_(c)longdoublelong double
complex types are structures with.real and.imag members (inthat order).
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 be8,16,32,64, 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. Whichbit-widths are available is platform dependent. The bolded bit-widthsare usually available on all platforms.
For help in printing, the following strings are defined as the correctformat specifier in printf and related commands.
NPY_LONGLONG_FMT,NPY_ULONGLONG_FMT,NPY_INTP_FMT,NPY_UINTP_FMT,NPY_LONGDOUBLE_FMT