A little encoding cache benchmark.


Current Code:
=============

import sys

def _fscodec():
    encoding = sys.getfilesystemencoding()
    errors = sys.getfilesystemencodeerrors()

    def fsencode(filename):
        filename = fspath(filename)  # Does type-checking of `filename`.
        if isinstance(filename, str):
            return filename.encode(encoding, errors)
        else:
            return filename

    def fsdecode(filename):
        filename = fspath(filename)  # Does type-checking of `filename`.
        if isinstance(filename, bytes):
            return filename.decode(encoding, errors)
        else:
            return filename

    return fsencode, fsdecode

fsencode, fsdecode = _fscodec()
del _fscodec

---------

import os

%timeit os.fsdecode(b'\xc3\xa9')
The slowest run took 21.59 times longer than the fastest. This could mean that an intermediate result is being cached.
1000000 loops, best of 3: 449 ns per loop

%timeit os.fsencode('é')
The slowest run took 24.20 times longer than the fastest. This could mean that an intermediate result is being cached.
1000000 loops, best of 3: 412 ns per loop


Modified Code:
==============

from sys import getfilesystemencoding, getfilesystemencodeerrors

def fsencode(filename):
    filename = fspath(filename)  # Does type-checking of `filename`.
    if isinstance(filename, str):
        return filename.encode(getfilesystemencoding(),
                               getfilesystemencodeerrors())
    else:
        return filename

def fsdecode(filename):
    filename = fspath(filename)  # Does type-checking of `filename`.
    if isinstance(filename, bytes):
        return filename.decode(getfilesystemencoding(),
                               getfilesystemencodeerrors())
    else:
        return filename

---------

import os

%timeit os.fsdecode(b'\xc3\xa9')
The slowest run took 15.88 times longer than the fastest. This could mean that an intermediate result is being cached.
1000000 loops, best of 3: 541 ns per loop

%timeit os.fsencode('é')
The slowest run took 19.32 times longer than the fastest. This could mean that an intermediate result is being cached.
1000000 loops, best of 3: 502 ns per loop


Result:
=======

Cache is a 17% speed up optimization.