the underscore of python

Question

def host(self):
    """ Return user host """
    _ = self._request.getText
    host = self.isCurrentUser() and self._cfg.show_hosts and self._request.remote_addr
    return host or _("<unknown>")

for this code ， _ is represent the getText function of _request . and i found _ sometimes represent for the last output of the command .

but i wonder why not use self._request.getText("") directly. and if i replace the _ with another variable,it still work . is there any difference ?

thanks for answer me .

The former question is also a duplicate of the latter, which predates either of these by over a year — Air, Feb 07 '14 at 17:45

score 4 · Answer 1 · answered Feb 15 '11 at 07:36

4

It's mostly a matter of convention. When your application is subject to i18n (internationalization), almost all your (display) strings go through a function to turn them into the proper language. Having a long function name for that will make the code unreadable, so naming it _ has become sort of a convention. (Also, some of the tools that help with i18n can look at your source code, recognize _("key") and make a list of keys that you need to translate.

answered Feb 15 '11 at 07:36

Ulrich Schwarz

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9

Also in non i18n-related contexts, the `_` variable is often used as a throw-away variable, it means that its value is of no importance for the programmer and will be discarded. Example: `for _ in range(0, 10):`. – Andrea Spadaccini Feb 15 '11 at 07:47

score 2 · Answer 2 · edited May 23 '17 at 12:04

_ is used in Python both as a throw-value variable, which are sometimes useful when you are using python interpreter as a calculator and you want the result of the last expression.

>>> 22.0/7
3.1428571428571428
>>> _ * 42

But using _ for a throw away variable is not really a good practice. It tends to confuse people a lot. Instead use a temp variable name.

There seems to be practice of assigning _ to a Factory class which produces i18n message. It is more of a convention and practice than anything of significant.

Following SO question is almost the same as yours.

the underscore of python

2 Answers2

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