Why would someone pass a string through an empty function instead of using the string directly in Python?
Question:
I am working through some old code for a tKinter GUI and at the top of their code they create the following definition:
def _(text):
return text
The code then proceeds to use the _ function around almost all of the strings being passed to the tKinter widgets. For example:
editmenu.add_command(label=_("Paste"), command=parent.onPaste)
Is there a reason for using the function here as opposed to just passing the string?
I’ve removed the _ function from around a few of the strings and haven’t run into any issues. Just curious if this has a real purpose.
Answers:
This is a stub for a pattern typically used for internationalization. The pattern is explicitly documented at https://docs.python.org/3/library/gettext.html#deferred-translations
_("Foo") is intended to have _ look up the string Foo in the current user’s configured language.
Putting the stub in now — before any translation tables have actually been built — makes it easy to search for strings that need to be translated, and avoids folks needing to go through the software figuring out which strings are intended for system-internal vs user-visible uses later. (It also helps guide programmers to avoid making common mistakes like using the same string constants for both user-visible display and save file formats or wire communications).
Understanding this is important, because it guides how this should be used. Don’t use _("Save %s".format(name)); instead, use _("Save %s").format(filename) so the folks who are eventually writing translation tables can adjust the format strings, and so those strings don’t need to have user-provided content (which obviously can’t be known ahead-of-time) within them.
I am working through some old code for a tKinter GUI and at the top of their code they create the following definition:
def _(text):
return text
The code then proceeds to use the _ function around almost all of the strings being passed to the tKinter widgets. For example:
editmenu.add_command(label=_("Paste"), command=parent.onPaste)
Is there a reason for using the function here as opposed to just passing the string?
I’ve removed the _ function from around a few of the strings and haven’t run into any issues. Just curious if this has a real purpose.
This is a stub for a pattern typically used for internationalization. The pattern is explicitly documented at https://docs.python.org/3/library/gettext.html#deferred-translations
_("Foo") is intended to have _ look up the string Foo in the current user’s configured language.
Putting the stub in now — before any translation tables have actually been built — makes it easy to search for strings that need to be translated, and avoids folks needing to go through the software figuring out which strings are intended for system-internal vs user-visible uses later. (It also helps guide programmers to avoid making common mistakes like using the same string constants for both user-visible display and save file formats or wire communications).
Understanding this is important, because it guides how this should be used. Don’t use _("Save %s".format(name)); instead, use _("Save %s").format(filename) so the folks who are eventually writing translation tables can adjust the format strings, and so those strings don’t need to have user-provided content (which obviously can’t be known ahead-of-time) within them.