# PyHash API

See also the `PyTypeObject.tp_hash` member and Hashing of numeric types.

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.

PyHASH_MODULUS

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

  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.

  Added in version 3.13.

PyHASH_IMAG

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

  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).

  const int hash_bits

    Internal size of the hash value in bits.

  const int seed_bits

    Size of seed input in bits.

  Added in version 3.4.

PyHash_FuncDef *PyHash_GetFuncDef(void)

  Get the hash function definition.

  See also

  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.

  CPython implementation detail: In CPython, it is equivalent to `Py_HashPointer()`.

  Added in version 3.13.