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Python Enhancement Proposals

PEP 332 – Byte vectors and String/Unicode Unification

Skip Montanaro <skip at>
Standards Track

Table of Contents


This PEP outlines the introduction of a raw bytes sequence object and the unification of the current str and unicode objects.

Rejection Notice

This PEP is rejected in this form. The author has expressed lack of time to continue to shepherd it, and discussion on python-dev has moved to a slightly different proposal which will (eventually) be written up as a new PEP. See the thread starting at


Python’s current string objects are overloaded. They serve both to hold ASCII and non-ASCII character data and to also hold sequences of raw bytes which have no reasonable interpretation as displayable character sequences. This overlap hasn’t been a big problem in the past, but as Python moves closer to requiring source code to be properly encoded, the use of strings to represent raw byte sequences will be more problematic. In addition, as Python’s Unicode support has improved, it’s easier to consider strings as ASCII-encoded Unicode objects.

Proposed Implementation

The number in parentheses indicates the Python version in which the feature will be introduced.

  • Add a bytes builtin which is just a synonym for str. (2.5)
  • Add a b"..." string literal which is equivalent to raw string literals, with the exception that values which conflict with the source encoding of the containing file not generate warnings. (2.5)
  • Warn about the use of variables named “bytes”. (2.5 or 2.6)
  • Introduce a bytes builtin which refers to a sequence distinct from the str type. (2.6)
  • Make str a synonym for unicode. (3.0)

Bytes Object API



  • Can this be accomplished before Python 3.0?
  • Should bytes objects be mutable or immutable? (Guido seems to like them to be mutable.)


Last modified: 2023-09-09 17:39:29 GMT