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16.5.2 Python
-------------

RPMs
     python

Ubuntu packages
     python

File extension
     ‘py’

String syntax
     ‘'abc'’, ‘u'abc'’, ‘r'abc'’, ‘ur'abc'’,
     ‘"abc"’, ‘u"abc"’, ‘r"abc"’, ‘ur"abc"’,
     ‘'''abc'''’, ‘u'''abc'''’, ‘r'''abc'''’, ‘ur'''abc'''’,
     ‘"""abc"""’, ‘u"""abc"""’, ‘r"""abc"""’, ‘ur"""abc"""’

gettext shorthand
     ‘_('abc')’ etc.

gettext/ngettext functions
     ‘gettext.gettext’, ‘gettext.dgettext’, ‘gettext.ngettext’,
     ‘gettext.dngettext’, also ‘ugettext’, ‘ungettext’

textdomain
     ‘gettext.textdomain’ function, or ‘gettext.install(DOMAIN)’
     function

bindtextdomain
     ‘gettext.bindtextdomain’ function, or
     ‘gettext.install(DOMAIN,LOCALEDIR)’ function

setlocale
     not used by the gettext emulation

Prerequisite
     ‘import gettext’

Use or emulate GNU gettext
     emulate

Extractor
     ‘xgettext’

Formatting with positions
     ‘'...%(ident)d...' % { 'ident': value }’
     ‘'...{ident}...'.format(ident=value)’
     ‘'...{0}...{1}...'.format(value0,value1)’
     ‘'...{}...{}...'.format(value0,value1)’

Portability
     fully portable

po-mode marking
     --

   An example is available in the ‘examples’ directory: ‘hello-python’.

   A note about format strings: Python supports format strings with
unnamed arguments, such as ‘'...%d...'’, and format strings with named
arguments, such as ‘'...%(ident)d...'’.  The latter are preferable for
internationalized programs, for two reasons:

   • When a format string takes more than one argument, the translator
     can provide a translation that uses the arguments in a different
     order, if the format string uses named arguments.  For example, the
     translator can reformulate
          "'%(volume)s' has only %(freespace)d bytes free."
     to
          "Only %(freespace)d bytes free on '%(volume)s'."
     Additionally, the identifiers also provide some context to the
     translator.

   • In the context of plural forms, the format string used for the
     singular form does not use the numeric argument in many languages.
     Even in English, one prefers to write ‘"one hour"’ instead of ‘"1
     hour"’.  Omitting individual arguments from format strings like
     this is only possible with the named argument syntax.  (With
     unnamed arguments, Python - unlike C - verifies that the format
     string uses all supplied arguments.)

   A note about f-strings (PEP 498): ‘xgettext’
   • syntactically recognizes f-strings,
   • is able to extract f-strings that contain no sub-expressions.
However, ‘xgettext’ does not extract f-strings marked for translation
that contain sub-expressions.  This will not work as expected:
     _(f"The file {file[i]} does not exist.")
because the translator is generally not a programmer and should thus not
be confronted with expressions from the programming language.

Related software
----------------

   An internationalization system based on GNU gettext and PO files is
Babel (https://babel.pocoo.org/).