On Wednesday, February 4, 2015 at 8:14:29 PM UTC+5:30, Albert-Jan Roskam wrote: > ----- Original Message ----- > > > From: Chris Angelico > > Sent: Wednesday, February 4, 2015 3:24 PM > > Subject: Re: meaning of: line, = > > > > On Thu, Feb 5, 2015 at 1:08 AM, ast wrote: > >> I dont understand why there is a comma just after line in the following > >> command: > >> > >> line, = plt.plot(x, np.sin(x), '--', linewidth=2) > >> > >> > >> I never saw that before > >> > >> Found here: > >> > > http://matplotlib.org/examples/lines_bars_and_markers/line_demo_dash_control.html > >> > > > > That's a slightly unusual form of unpacking. Compare: > > > > def get_values(): > > return 5, 7, 2 > > > > x, y, z = get_values() > > > > This is like "x = 5; y = 7; z = 2", because it unpacks the > > function's > > return value into those three targets. > > > > What you have is exactly the same, except that it has only one target. > > So it's expecting plt.plot() to return an iterable with exactly one > > thing in it, and it'll unpack it and put that thing into line: > > > > def get_packaged_value(): > > return [42] > > > > x, = get_packaged_value() > > > > This is equivalent to "x = 42". I don't know matplotlib, so I > > don't > > know what it's returning or why, but as long as it's iterable and > > yields exactly one thing, this will work. > > > > I have also never seen this before, but perhaps this: > > >>> f = lambda: [42] > >>> result, = f() > >>> result > 42 > > ... is slightly cleaner than this: > >>> result = f()[0] > >>> result > 42
Well its cryptic and confusing (to me at least) And is helped by adding 2 characters: (result,) = f() instead of result, = f() -- https://mail.python.org/mailman/listinfo/python-list
