EC
BytesWarning
PythonWARNINGCommonWarning

Bytes or buffer compared with str

Quick Answer

Run python -bb to promote BytesWarning to errors during development to catch all bytes/str mixing.

Production Risk

Low.

What this means

Raised when bytes or bytearray objects are compared with str, or when bytes are used in a context that expects str. Enabled by running Python with the -b flag.

Why it happens
  1. 1bytes == str comparison that always returns False
  2. 2bytes object passed to a function expecting str

Fix

Use -bb during development to catch all byte/str mixing

Use -bb during development to catch all byte/str mixing
# Development: promote to error
python -bb my_script.py

# Fix: decode bytes explicitly
data = response.content        # bytes
text = data.decode('utf-8')    # str — safe to compare with str

Why this works

-bb turns BytesWarning into a BytesWarning exception, making every mixing site visible.

Same error in other languages
UnicodeWarningin Python→
Sources

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