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zlib.adler32()

checksums

Computes the Adler-32 checksum — faster than CRC-32 but weaker; it can be computed in pieces.

Syntax

zlib.adler32(data[, value])

The zlib format itself uses it at the end of a stream, but crc32 is the usual choice for your own data: Adler-32 is weak at catching errors in messages only a few bytes long. Its starting value is 1, not 0 — adler32(b'') == 1 — so when computing in pieces, omit the second argument on the first call instead of passing 0. It is not a cryptographic hash.

Examples

import zlib
print(zlib.adler32(b''), zlib.crc32(b''))  # → 1 0
running = zlib.adler32(b'hel')
print(zlib.adler32(b'lo', running) == zlib.adler32(b'hello'))  # → True
print(zlib.adler32(b'lo', 0) == zlib.adler32(b'lo'))  # → False — начало не с 0

See also

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