[IPython-dev] Using argparse for %magics

Prabhu Ramachandran prabhu@aero.iitb.ac...
Sat Apr 11 00:54:21 CDT 2009

On 04/07/09 23:41, Fernando Perez wrote:
> On Sun, Apr 5, 2009 at 1:50 AM, Robert Kern <robert.kern@gmail.com> wrote:
>> I have updated my personal collection of %magics today:
> Just an initial reply before we dive into this, since I'm going
> semi-offline for a couple of days.
> +1 to argparse for this, as long as we carry it (not as a separate
> dependency).  I've been thinking about cleaning up the magics as part
> of the core reorg Brian will work on soon, and this would fit nicely
> into that idea.

Just my vote that it would be nice if these (the print_traits esp.) were 
available in the standard IPython.

I also have a suggestion regarding magics in general.  I always found 
IPython's timeit *much* more convenient than the standard timeit module. 
  However, IPython's timeit is only usable from IPython and not from a 
standalone Python script.  I think all magics (that are of use outside 
of IPython) ought to be refactored to be usable outside of the 
interactive IPython shell.

I also think I have found a little bug(?) in the timeit magic 
implementation.  Here is a patch (this is off the 0.9.1 release):

--- Magic.py.orig       2009-04-11 11:14:49.000000000 +0530
+++ Magic.py    2009-04-11 11:15:15.000000000 +0530
@@ -1815,9 +1815,9 @@
              # determine number so that 0.2 <= total time < 2.0
              number = 1
              for i in range(1, 10):
-                number *= 10
                  if timer.timeit(number) >= 0.2:
+                number *= 10

          best = min(timer.repeat(repeat, number)) / number

The rationale is as follows.  Lets say you have a function that takes 2 
seconds to evaluate.  With the original code you are going to run that 
function 10 times regardless of the fact that it already takes 2 seconds 
and with the original code, timing this will take at least 60 seconds 
(with repeat=3) which is way too much.  Here is a simple test case:

import time
def f():
     print "f"

%timeit f()


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