all Python 3hashlibfunction

hashlib.sha256()

hashing

Creates a SHA-256 hash object. A cryptographically strong algorithm. Use it for data integrity checks and digital signatures.

Syntax

hashlib.sha256(data=b'')

Being collision-resistant does not make SHA-256 suitable for passwords: it is fast, so a dictionary attack runs millions of hashes per second — use hashlib.pbkdf2_hmac() or hashlib.scrypt(), which are deliberately slow and salted. When comparing secret digests, use hmac.compare_digest() rather than ==, since a plain comparison bails out at the first differing byte and leaks timing information.

Examples

import hashlib
h = hashlib.sha256(b'secret data')
print(len(h.hexdigest()))  # → 64 — шестнадцатеричных символов

import hashlib
# постепенная загрузка большого файла: память не зависит от его размера
with open('bigfile.bin', 'wb') as f:
    f.write(b'x' * 200_000)
h = hashlib.sha256()
with open('bigfile.bin', 'rb') as f:
    for chunk in iter(lambda: f.read(65536), b''):
        h.update(chunk)
print(h.hexdigest() == hashlib.sha256(b'x' * 200_000).hexdigest())  # → True

See also

Common errors

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