How to make python's argparse generate Non-English text?

Question

The argparse module "automatically generates help and usage messages". I can give Non-English names to the arguments and provide Non-English help texts; but the help output then becomes a mixture of at least two languages, because terms like usage, positional arguments, optional arguments and show this help message and exit are automatically generated in English.

How can I replace this English output with translations?

Preferably, I would like to provide the translations within the script, so that the script generates the same output wherever it is started.

Edit: Based on the answer by Jon-Eric, here an example with his solution:

import gettext

def Übersetzung(Text):
    Text = Text.replace("usage", "Verwendung")
    Text = Text.replace("show this help message and exit",
                        "zeige diese Hilfe an und tue nichts weiteres")
    Text = Text.replace("error:", "Fehler:")
    Text = Text.replace("the following arguments are required:",
                        "Die folgenden Argumente müssen angegeben werden:")
    return Text
gettext.gettext = Übersetzung

import argparse

Parser = argparse.ArgumentParser()
Parser.add_argument("Eingabe")
Argumente = Parser.parse_args()

print(Argumente.Eingabe)

saved as Beispiel.py gives with python3 Beispiel.py -h the following help output:

Verwendung: Beispiel.py [-h] Eingabe

positional arguments:
  Eingabe

optional arguments:
  -h, --help  zeige diese Hilfe an und tue nichts weiteres

Answer 1

One way, from this post by Peter Otten:

I don't know much about gettext, but the following suggests that most strings in argparse are properly wrapped:

$ cat localize_argparse.py

import gettext

def my_gettext(s):
    return s.upper()
gettext.gettext = my_gettext

import argparse

if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument("-V", action="version")
    args = parser.parse_args()

$ python localize_argparse.py -h USAGE: localize_argparse.py [-h] [-V]

OPTIONAL ARGUMENTS:   -h, --help  SHOW THIS HELP MESSAGE AND EXIT   -V
show program's version number and exit

The workaround for the "-V" option would be to add the help message explicitly

parser.add_argument("-V", ..., help=_("show..."))

You still have to provide all translations yourself.

Answer 2

argparse uses the gettext API inspired by GNU gettext. You can use this API to integrate your translation of argparse in a relatively clean manner.

To do so, call the following code before argparse outputs any text (but possibly after import argparse):

import gettext

# Use values that suit your project instead of 'argparse' and 'path/to/locale'
gettext.bindtextdomain('argparse', 'path/to/locale')
gettext.textdomain('argparse')

In order for this solution to work, your translation of argparse must be located at path/to/locale/ll/LC_MESSAGES/argparse.mo where ll is the code of the current language (for example de; can be configured for example by setting the environment variable LANGUAGE).

How do you generate the .mo file?

1. pygettext --default-domain=argparse /usr/local/lib/python3.5/argparse.py
   • Use the actual location of argparse.py
   • Creates the file argparse.pot
2. cp argparse.pot argparse-ll.po
   • Use an actual language code instead of ll
3. Fill in the missing translation strings in argparse-ll.po
4. msgfmt argparse-ll.po -o locale/ll/LC_MESSAGES/argparse.mo

See gettext documentation for details about creating .mo file.

I have published these instructions in more detail in README.md of my Czech translation of argparse.

Answer 3

Here is a solution with French translation, where one creates a conversion dict that holds the translation for the encountered English keywords

def convertArgparseMessages(s):
    subDict = \
    {'positional arguments':'Arguments positionnels',
    'optional arguments':'Arguments optionnels',
    'show this help message and exit':'Affiche ce message et quitte'}
    if s in subDict:
        s = subDict[s]
    return s
gettext.gettext = convertArgparseMessages
import argparse

Answer 4

I was faced with a similar problem. Almost all messages will translated properly doing as described in post 5, but not the help messages added with parser.add_argument(). You can solve the problem by using non-class-based gettext for argparse and class-based gettext for the app. Have a look at app3.py in https://github.com/jmo3300/py01_i18n_01