On Wed, 10 Feb 2010 10:08:47 -0500, John Posner wrote: >> This won't work correctly, because old_f still tries to refer to itself >> under the name "f", and things break very quickly. > > They didn't break immediately for me -- what am I missing?:
The original function f doesn't try to refer to itself in any way. With no recursive call or access, it doesn't matter what f is named. See this example instead: >>> def f(x): ... if x < 0: ... print "original" ... return f(-x) ... else: ... return x+1 ... >>> f(2) 3 >>> f(-2) original 3 >>> >>> old_f = f >>> def f(x): ... if x > 0: ... return old_f(-x) ... else: ... return x ... >>> f(-1) -1 >>> f(1) original original original original original original [...] File "<stdin>", line 3, in f File "<stdin>", line 4, in f File "<stdin>", line 3, in f RuntimeError: maximum recursion depth exceeded -- Steven -- http://mail.python.org/mailman/listinfo/python-list
