all Python 3hashlibfunction

hashlib.new()

hashing

A generic constructor that builds a hash object from the algorithm name as a string: hashlib.new('sha256') is the same as hashlib.sha256().

Syntax

hashlib.new(name, data=b'', *, usedforsecurity=True)

It is meant for when the algorithm comes from a config file or a command-line argument; when the name is known in advance, the named constructor is faster and safer. The name is case-insensitive ('SHA256' works too), and an unknown one raises ValueError (the message varies by version: in 3.15 it is “unsupported hash algorithm”). The set of names depends on the OpenSSL build: only hashlib.algorithms_guaranteed is always there, while algorithms_available differs between machines — an algorithm you found locally may be missing on the server.

Examples

import hashlib
h = hashlib.new('SHA256', b'abc')
print(h.name)  # → sha256
print(h.hexdigest()[:16])  # → ba7816bf8f01cfea

import hashlib
try:
    hashlib.new('sha257')
except ValueError as e:
    print(e)  # → sha257 — «unsupported hash type», с 3.15 «unsupported hash algorithm»

See also

Common errors

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