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bytes.startswith

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Check whether the bytes start with a prefix.

Syntax

b.startswith(...)

The prefix must be a bytes-like object, or a tuple of them: calling b'GET /'.startswith('GET') with a text string raises TypeError, a classic slip when parsing network data. A tuple means 'any of these', and the optional start and end narrow the region without building a sliced copy, which beats b[2:5] == prefix on large buffers. It only tests; to strip the prefix use removeprefix (Python 3.9+).

Examples

print(b'hello'.startswith(b'he'))   # → True
print(b'hello'.startswith((b'hi', b'he')))   # → True
print(b'hello'.startswith(b'llo', 2))   # → True
print(b'GET /index.html'.startswith(b'GET '))   # → True
print(b'hello'.startswith(b''))   # → True
print(b'hello'.startswith('he'))   # → TypeError

See also

Common errors

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