Quick start guide

Installing polib

polib requires python 2.7 or superior.

There are several ways to install polib, this is explained in the installation section.

For the impatient, the easiest method is to install polib via pip, just type:

pip install polib

Some basics about gettext catalogs

A gettext catalog is made up of many entries, each entry holding the relation between an original untranslated string and its corresponding translation.

All entries in a given catalog usually pertain to a single project, and all translations are expressed in a single target language. One PO file entry has the following schematic structure:

#  translator-comments
#. extracted-comments
#: reference...
#, flag...
msgid untranslated-string
msgstr translated-string

A simple entry can look like this:

#: lib/error.c:116
msgid "Unknown system error"
msgstr "Error desconegut del sistema"

polib has two main entry points for working with gettext catalogs:

References * Gettext Manual * PO file format * MO file format

Loading existing catalogs

Loading a catalog and detecting its encoding

Here the encoding of the po file is auto-detected by polib (polib detects it by parsing the charset in the header of the pofile):

import polib
po = polib.pofile('path/to/catalog.po')

Loading a catalog and specifying explicitly the encoding

For some reason you may want to specify the file encoding explicitly (because the charset is not specified in the po file header for example), to do so:

import polib
po = polib.pofile(

Loading an mo file

In some cases you can be forced to load an mo file (because the po file is not available for example), polib handles this case:

import polib
mo = polib.mofile('path/to/catalog.mo')

As for po files, mofile also allows specifying the encoding explicitly.

Creating po catalogs from scratch

polib allows you to create catalog from scratch, this can be done with the POFile class, for example to create a simple catalog you could do:

import polib

po = polib.POFile()
po.metadata = {
    'Project-Id-Version': '1.0',
    'Report-Msgid-Bugs-To': 'you@example.com',
    'POT-Creation-Date': '2007-10-18 14:00+0100',
    'PO-Revision-Date': '2007-10-18 14:00+0100',
    'Last-Translator': 'you <you@example.com>',
    'Language-Team': 'English <yourteam@example.com>',
    'MIME-Version': '1.0',
    'Content-Type': 'text/plain; charset=utf-8',
    'Content-Transfer-Encoding': '8bit',

This snippet creates an empty pofile, with its metadata, and now you can add you entries to the po file like this:

entry = polib.POEntry(
    occurrences=[('welcome.py', '12'), ('anotherfile.py', '34')]

To save your file to the disk you would just do:


And to compile the corresponding mo file:


More examples

Iterating over entries

Iterating over all entries (by default POFiles contains all catalog entries, even obsolete and fuzzy entries):

import polib

po = polib.pofile('path/to/catalog.po')
for entry in po:
    print(entry.msgid, entry.msgstr)

Iterating over all entries except obsolete entries:

import polib

po = polib.pofile('path/to/catalog.po')
valid_entries = [e for e in po if not e.obsolete]
for entry in valid_entries:
    print(entry.msgid, entry.msgstr)

Iterating over translated entries only:

import polib

po = polib.pofile('path/to/catalog.po')
for entry in po.translated_entries():
    print(entry.msgid, entry.msgstr)

And so on… You could also iterate over the list of POEntry objects returned by the following POFile methods:

Getting the percent of translated entries

import polib

po = polib.pofile('path/to/catalog.po')

Compiling po to mo files and reversing mo files to po files

Compiling a po file:

import polib

po = polib.pofile('path/to/catalog.po')
# to get the binary representation in a variable:
modata = po.to_binary()
# or to save the po file as an mo file

Reverse a mo file to a po file:

mo = polib.mofile('path/to/catalog.mo')
# to get the unicode representation in a variable, just do:
podata = unicode(mo)
# or to save the mo file as an po file