Python complaints

Michael Hudson mwh21 at cam.ac.uk
Tue Nov 30 16:31:41 CET 1999


wware-nospam at world.std.com (Will Ware) writes:

> Will Ware wrote:
> > I find myself grumbling about having to type "x = x + 1". The really
> > clean thing to do, given that integers are objects, would be to define
> > increment and decrement methods, so you'd type something like "i.incr()".
> 
> Jesse D. Sightler (jsight at mindspring.com) wrote:
> > Wouldn't this be impossible, since Integers are also immutable?  So, eg,
> > i.incr() could only return an incremented version of i, but not actually
> > increment i?
> 
> Right, this is what Gordon was pointing out. A "++" method could not
> magically reach out of its object, find the "i" variable, and bind it
> to the incremented value. 

Hate to be awkward, but when it comes to things like this, there's
very little like this that can't be done in Python!

>>> def incr(var):
	try:
		raise 1/0
	except ZeroDivisionError:
		import sys,dis
		f = sys.exc_traceback.tb_frame.f_back
		loadins = f.f_code.co_code[f.f_lasti - 3:f.f_lasti]
		loadop = ord(loadins[0])
		name = dis.opname[loadop]
		loadarg = ord(loadins[1]) + 256*ord(loadins[2])
		vname = f.f_code.co_names[loadarg]
		f.f_locals[vname] = f.f_locals[vname] + 1

		
>>> x=1
>>> incr(x)
>>> x
2

well, it works in the IDLE shell window...

I'll stop now ;-).

> Something like this could be accomplished by tinkering with Python's
> parser, but that wouldn't be a great idea.

As above, not necessary.

> A lot of work for something that would never find wide acceptance.

That much is true!

Cheers,
Michael




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