all Python 3Byte sequencesfunction

bytes.index

bytes — search

Like find, but raises ValueError if not found.

Syntax

b.index(...)

Choosing between index and find is a policy decision: index when a missing subsequence means broken data and failing loudly is right, find when absence is a normal case you branch on. If you wrap it in try, catch ValueError specifically, not Exception — a blanket catch would also swallow the TypeError from accidentally passing a str.

Examples

print(b'banana'.index(b'na'))   # → 2
print(b'banana'.index(b'na', 3))   # → 4
print(b'banana'.index(ord('n')))   # → 2
print(b'banana'.index(b'z'))   # → ValueError
print(b'banana'.find(b'z'))   # → -1

See also

Common errors

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