all Python 3Exceptionsexception

UnicodeDecodeError

built-in exceptions

Bytes could not be decoded into a string, e.g. b'\xff'.decode('utf-8').

Syntax

raise UnicodeDecodeError

The bytes are rarely the real problem — the guessed encoding usually is: before Python 3.15, open() without encoding= falls back to the platform default, so a UTF-8 file that reads fine on Linux blows up on a Windows box using cp1251. Catching the exception seldom helps; pass encoding='utf-8' explicitly, or errors='replace'/'ignore' when broken bytes are genuinely expected. The instance carries encoding, object, start, end and reason, which pinpoint the exact byte where the decoder gave up.

Examples

try:
    b'\xff'.decode('utf-8')
except UnicodeDecodeError as e:
    print(type(e).__name__)   # → UnicodeDecodeError

See also

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