Comments on: Small Python Interactive Interface Trick

By: hmarr

hmarr — Mon, 01 Dec 2008 18:10:22 +0000

lorg:
Of course! Clearly I didn’t have my head screwed on properly when I wrote that!

By: lorg

lorg — Mon, 01 Dec 2008 09:45:04 +0000

llr:
No, it isn’t.
In your code snippet, t holds the result of a single call to test().
However, in the interactive prompt when you do
>>> x [enter]
x.__repr__() gets called.
So, in my version, each time you try to view t, you actually call NoParens.__repr__, and that means a new call to test. I believe this would be clearer if test() returned time.time():

[python]
In [2]: import noparens

In [3]: import time

In [4]: def test():
…: return time.time()
…:

In [5]: t = noparens.NoParens(test)

In [6]: t
Out[6]: 1228124415.74

In [7]: t
Out[7]: 1228124416.37
[/python]

By: llr

llr — Mon, 01 Dec 2008 08:44:06 +0000

Is this your script’ purpose as I think? like below:

>>> def test():
… return 4**4
…
>>> t = test()
>>> t
256
>>>

By: lorg

lorg — Mon, 01 Dec 2008 07:15:41 +0000

hmarr:
Nice idea!
However, to do what you propose you don’t need to change the code of NoParens, you can already use it as is. Any callable object may be used as a decorator.

By: hmarr

hmarr — Mon, 01 Dec 2008 02:13:34 +0000

Could work nicely as a decorator too:

def noparens(func):
class ReprFunc(object):
def __init__(self, f):
self.f = f
def __repr__(self):
return str(self.f())
def __call__(self, *args, **kwargs):
return self.f(*args, **kwargs)
return ReprFunc(func)

Usage:

@noparens
def foo():
return 6*3

>>> foo
18

By: lorg

lorg — Sun, 30 Nov 2008 23:05:30 +0000

Knorby:
Two reasons:
1. I didn’t know about it, thanks :)
2. Even if I had, I couldn’t have used it. I was using an embedded Python shell, that doesn’t work with IPython. Although integrating it is possible, that work wasn’t done.
That made using this shell even more painful, because I didn’t have all the fancy IPython features, such as tab-completion. That pain made this trick even more useful than it normally is.

By: knorby

knorby — Sun, 30 Nov 2008 20:03:27 +0000

Why not just use %autocall from the IPython magic commands? You wouldn't be able to do everything that you can do with your trick (just calling "t" would work the same, but not "t,t,t"), but it would require a whole lot less effort.

By: lorg

lorg — Sun, 30 Nov 2008 14:56:51 +0000

Thanks :)
The best example would be a debugger:
Given a single_step() function, use s as a shorthand, and maybe r for run(), and p for print_state().
Given these, debugging with a Python interactive prompt gets a little bit easier. Especially when you can do:
s,s,s,p,r

By: arkon

arkon — Sun, 30 Nov 2008 11:26:14 +0000

hey man
glad you are back to write posts :)
can you give a more practical example maybe?