Q:

make python sort / compare the same way as GNU sort

It seems after some first tests, that Python is using the same sorting order as Linux sort (gnu sort) with the C sorting order (if the locale is set to "C").
However I'd like to be able to write  Python code that is sorting and comparing the same way as gnu sort depending on the locale.
Small example code to illustrate the issue:
import os 
import subprocess

words = [
    "Abd",
    "éfg",
    "aBd",
    "aBd",
    "zzz",
    "ZZZ",
    "efg",
    "abd",
    "fff",
    ]

with open("tosort", "w") as fout:
    for word in words:
        fout.write(word + "\n")

os.environ["LC_ALL"] = "en_US.UTF-8" 
proc = subprocess.Popen(["sort", "tosort"], stdout=subprocess.PIPE)
sort_en_utf = proc.stdout.read().decode('utf-8').split()

os.environ["LC_ALL"] = "C" 
proc = subprocess.Popen(["sort", "tosort"], stdout=subprocess.PIPE) 
sort_c = proc.stdout.read().decode('utf-8').split()

os.environ["LC_ALL"] = "en_US.UTF-8"
sort_py = sorted(words)

for row in zip(sort_en_utf, sort_c, sort_py):
    print(" ".join(row))

If above code is run I get following output:
abd Abd Abd
aBd ZZZ ZZZ
aBd aBd aBd
Abd aBd aBd
efg abd abd
éfg efg efg
fff fff fff
zzz zzz zzz
ZZZ éfg éfg

column 1 is the sorting / comparing order that I'd like to have in my python code if the locale is "en_US.UTF-8" column 2 and 3 show, that python sorts the same way as linux' sort if the locale is set to "C".
So I'd also like, to know whether there is a way to have:
"éfg" < "fff" yield True. I don't insist on a compare operator I can also call a function.
but the ordering result should be considering  the current locale.

A:

Hmmm somehow I overlooked this:
The sorting doc of python https://docs.python.org/3.5/howto/sorting.html mentions in the last section "Odds and Ends" the function locale.strxfrm() (see https://docs.python.org/3.5/library/locale.html#locale.strxfrm ) as key function for sorting and locale.strcoll() as a comparison function.
So following modified code is almost OK, except that the comparison function does not return directly true / false, but this is OK in my context
import subprocess

words = [
    "Abd",
    "éfg",
    "aBd",
    "aBd",
    "zzz",
    "ZZZ",
    "efg",
    "abd",
    "fff",
    "sra",
    "ssa",
    "ssb",
    "stb",
    "ßaa",
    ]

val1 = "ßaa"
val2 = "ssb"

with open("tosort", "w") as fout:
    for word in words:
        fout.write(word + "\n")

os.environ["LC_ALL"] = "en_US.UTF-8"
proc = subprocess.Popen(["sort", "tosort"], stdout=subprocess.PIPE)
sort_en_utf = proc.stdout.read().decode('utf-8').split()

os.environ["LC_ALL"] = "C"
proc = subprocess.Popen(["sort", "tosort"], stdout=subprocess.PIPE)
sort_c = proc.stdout.read().decode('utf-8').split()

locale.setlocale(locale.LC_ALL, "en_US.UTF-8")
sort_py1 = sorted(words, key=lambda v: locale.strxfrm(v))
print("%r < %r = %s , but locale.strcoll(%r, %r) = %s for %s"
      % (val1, val2, val1 < val2, val1, val2,
         locale.strcoll(val1, val2), locale.getlocale())
      )

locale.setlocale(locale.LC_ALL, "C")
sort_py2 = sorted(words, key=lambda v: locale.strxfrm(v))
print("%r < %r = %s , but locale.strcoll(%r, %r) = %s for %s"
      % (val1, val2, val1 < val2, val1, val2,
         locale.strcoll(val1, val2), locale.getlocale())
      )

for row in zip(sort_en_utf, sort_py1, sort_c, sort_py2):
    print(" ".join(row))

The output would be
'ßaa' < 'ssb' = False , but locale.strcoll('ßaa', 'ssb') = -1 for ('en_US', 'UTF-8')
'ßaa' < 'ssb' = False , but locale.strcoll('ßaa', 'ssb') = 1 for (None, None)
abd abd Abd Abd
aBd aBd ZZZ ZZZ
aBd aBd aBd aBd
Abd Abd aBd aBd
efg efg abd abd
éfg éfg efg efg
fff fff fff fff
sra sra sra sra
ssa ssa ssa ssa
ßaa ßaa ssb ssb
ssb ssb stb stb
stb stb zzz zzz
zzz zzz ßaa ßaa
ZZZ ZZZ éfg éfg

