PyHash API#

See also the "PyTypeObject.tp_hash" member and Calculo del hash de tipos numéricos.

type Py_hash_t

Hash value type: signed integer.

Added in version 3.2.

type Py_uhash_t

Hash value type: unsigned integer.

Added in version 3.2.

Py_HASH_ALGORITHM

A numerical value indicating the algorithm for hashing of "str", "bytes", and "memoryview".

The algorithm name is exposed by "sys.hash_info.algorithm".

Added in version 3.4.

Py_HASH_FNV Py_HASH_SIPHASH24 Py_HASH_SIPHASH13

Numerical values to compare to "Py_HASH_ALGORITHM" to determine which algorithm is used for hashing. The hash algorithm can be configured via the configure "--with-hash-algorithm" option.

Added in version 3.4: Add "Py_HASH_FNV" and "Py_HASH_SIPHASH24".

Added in version 3.11: Add "Py_HASH_SIPHASH13".

Py_HASH_CUTOFF

Buffers of length in range "[1, Py_HASH_CUTOFF)" are hashed using DJBX33A instead of the algorithm described by "Py_HASH_ALGORITHM".

• A "Py_HASH_CUTOFF" of 0 disables the optimization.

• "Py_HASH_CUTOFF" must be non-negative and less or equal than 7.

32-bit platforms should use a cutoff smaller than 64-bit platforms because it is easier to create colliding strings. A cutoff of 7 on 64-bit platforms and 5 on 32-bit platforms should provide a decent safety margin.

This corresponds to the "sys.hash_info.cutoff" constant.

Added in version 3.4.

PyHASH_MODULUS

The Mersenne prime "P = 2**n -1", used for numeric hash scheme.

This corresponds to the "sys.hash_info.modulus" constant.

Added in version 3.13.

PyHASH_BITS

The exponent "n" of "P" in "PyHASH_MODULUS".

Added in version 3.13.

PyHASH_MULTIPLIER

Prime multiplier used in string and various other hashes.

Added in version 3.13.

PyHASH_INF

The hash value returned for a positive infinity.

This corresponds to the "sys.hash_info.inf" constant.

Added in version 3.13.

PyHASH_IMAG

The multiplier used for the imaginary part of a complex number.

This corresponds to the "sys.hash_info.imag" constant.

Added in version 3.13.

type PyHash_FuncDef

Hash function definition used by "PyHash_GetFuncDef()".

Py_hash_t (const hash)(const void, Py_ssize_t)

  Hash function.

const char *name

  Hash function name (UTF-8 encoded string).

  This corresponds to the "sys.hash_info.algorithm" constant.

const int hash_bits

  Internal size of the hash value in bits.

  This corresponds to the "sys.hash_info.hash_bits" constant.

const int seed_bits

  Size of seed input in bits.

  This corresponds to the "sys.hash_info.seed_bits" constant.

Added in version 3.4.

PyHash_FuncDef *PyHash_GetFuncDef(void)

Get the hash function definition.

Ver también:

 **PEP 456** "Secure and interchangeable hash algorithm".

Added in version 3.4.

Py_hash_t Py_HashPointer(const void *ptr)

Hash a pointer value: process the pointer value as an integer (cast it to "uintptr_t" internally). The pointer is not dereferenced.

The function cannot fail: it cannot return "-1".

Added in version 3.13.

Py_hash_t Py_HashBuffer(const void *ptr, Py_ssize_t len)

Compute and return the hash value of a buffer of len bytes starting at address ptr. The hash is guaranteed to match that of "bytes", "memoryview", and other built-in objects that implement the buffer protocol.

Use this function to implement hashing for immutable objects whose "tp_richcompare" function compares to another object's buffer.

len must be greater than or equal to "0".

This function always succeeds.

Added in version 3.14.

Py_hash_t PyObject_GenericHash(PyObject *obj)

Generic hashing function that is meant to be put into a type object's "tp_hash" slot. Its result only depends on the object's identity.

Detalles de implementación de CPython: In CPython, it is equivalent to "Py_HashPointer()".

Added in version 3.13.