[Python-Dev] Inconsistencies if locale and filesystem encodings are different (original) (raw)

M.-A. Lemburg mal at egenix.com
Thu Oct 7 18:35:09 CEST 2010

Victor Stinner wrote:

Hi,

A PYTHONFSENCODING environment variable was added to Python 3.2: issue #8622. This variable introduces an inconstency because the filesystem and the locale encodings can now be different. There are (at least) four issues related to this problem. We have 2 choices to fix these issues: (a) use the same encoding to encode and decode values (it can be different for each issue) (b) remove PYTHONFSENCODING variable and raise an error if locale and filesystem encodings are different (ensure that both encodings are the same) Even if choice (a) is not easy to implement, it is feasible and I already wrote some patches. I don't understand how Python interact with other programs who ignore the PYTHONFSENCODING environment variable. It's like Python uses its own "locale". Choice (b) looks easy to implement, but... there is the problem of Mac OS X. Mac OS X uses utf-8 encoding for the filesystem (and not the locale encoding), whereas it looks like the locale encoding is used for the command line arguments. See issue #4388 for more information. There is also maybe an useful usecase of the PYTHONFSENCODING, but I don't remember which one :-)

You have to differentiate between the meaning of a file system encoding and the locale:

A file system encoding defines how the applications interact with the file system.

A locale defines how the user expects to interact with the application.

It is well possible that the two are different. Mac OS X is just one example. Another common example is having a Unix account using the C locale (=ASCII) while working on a UTF-8 file system.

BTW: We added that because just like I/O encoding, you need to be able to override the setting determined by Python via locale introspection, which may be wrong. The env var is only meant as a way to solve encoding problems in special situations where the local cannot be used to determine the file system or input/output encoding.

-- Marc-Andre Lemburg eGenix.com

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