FNV (or Fowler-Noll-Vo is a non-cryptographic hash function.

Aside from code simplicity, this hash function is not particularly good at anything.

Python implementation

Below are self-contained implementations of the FNV hash function in Python. Feel free to grab one and copy-paste it into your projects.

FNV-1

This function reads a byte array and produces a U64 hash value.

In [2]:
def fnv1(buf: bytes) -> int:
    h = 14695981039346656037

    for b in buf:
        h *= 1099511628211
        h &= 0xFFFFFFFFFFFFFFFF  # 64-bit mask
        h ^= b

    return h
In [3]:
fnv1(b"Hello world")
fnv1(b"Hello wordl")
Out [3]:
13583674344491166159
Out [3]:
13583665548398140543

FNV-1a

This is the same as FNV-1, but the multiplication and XOR operations are swapped. This is done to improve avalanche effect.

In [4]:
def fnv1a(buf: bytes) -> int:
    h = 14695981039346656037

    for b in buf:
        h ^= b
        h *= 1099511628211
        h &= 0xFFFFFFFFFFFFFFFF  # 64-bit mask

    return h
In [5]:
fnv1a(b"Hello world")
fnv1a(b"Hello wordl")
Out [5]:
2815866345377719495
Out [5]:
2823738848634196455

References and useful links