Is a string formatter that pulls variables from its calling scope bad practice?

Question

I have some code that does an awful lot of string formatting, Often, I end up with code along the lines of:

\"...\".format(x=x, y=y, z=z, foo=foo, ...)
         


        

Answer 1

The good old mailman has a function _ that does exactly this thing:

def _(s):
    if s == '':
        return s
    assert s
    # Do translation of the given string into the current language, and do
    # Ping-string interpolation into the resulting string.
    #
    # This lets you write something like:
    #
    #     now = time.ctime(time.time())
    #     print _('The current time is: %(now)s')
    #
    # and have it Just Work.  Note that the lookup order for keys in the
    # original string is 1) locals dictionary, 2) globals dictionary.
    #
    # First, get the frame of the caller
    frame = sys._getframe(1)
    # A `safe' dictionary is used so we won't get an exception if there's a
    # missing key in the dictionary.
    dict = SafeDict(frame.f_globals.copy())
    dict.update(frame.f_locals)
    # Translate the string, then interpolate into it.
    return _translation.gettext(s) % dict

So if Barry Warsaw can do that, why can't we?