In Python after a function has already been declared can it be redefined without it being completely redefined. Could I for example create a function then add or remove a statement from it?
For example say I have this:
def func(x, y):
y = 2 * x
return yThen could I do something like this:
func() = func() - return ySo then the function would be only:
y = 2 * x
C:\windows\system32>python
Python 3.3.2 (v3.3.2:d047928ae3f6, May 16 2013, 00:06:53) [MSC v.1600 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> y=5
>>> def double1(x):
... print(y)
... y=x*2
... print(y)
...
>>> print(y)
5
>>> double1(25)
Traceback (most recent call last):
File "", line 1, in
File "", line 2, in double1
UnboundLocalError: local variable 'y' referenced before assignment
>>> def double2(x):
... y=x*2
... print(y)
...
>>> double2(25)
50
>>> print(y)
5
>>> def double3(x):
... global y
... y=x*2
... print(y)
...
>>> double3(13)
26
>>> print(y)
26C:\windows\system32>python
Python 3.3.2 (v3.3.2:d047928ae3f6, May 16 2013, 00:06:53) [MSC v.1600 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> def f(x):
... return x+1
...
>>> def g(x):
... return x+2
...
>>> print(f(1))
2
>>> print(g(1))
3
>>> f,g = g,f
>>> print(f(1))
3
>>> print(g(1))
2
>>> f=None
>>> print(f(1))
Traceback (most recent call last):
File "", line 1, in
TypeError: 'NoneType' object is not callableFirstly, the example given is ridiculous, because there is no benefit for having a function that's the same as another, except for the fact that it doesn't return a value. You can just not use the result in the caller. The overhead for returning a value is negligible, if not 0.
Secondly, a more general way of making functions out of other functions, is to have the larger function call the more specific functions it needs. The the user can call either the larger function, or the more specific function, depending on what is needed. The decorator's that SiCrane mentioned is a form of this.
code = \
"""
def func(x, y):
y = 2 * x
return y
"""
code = code.split('\n')
code.pop(); code.pop(0)
exec("\n".join(code))
func(3, 2) # 6
exec("\n".join(code[:2])) # Only first 2 lines, excluding return
func(3, 2) # None
But don't ever do this. 
In Python after a function has already been declared can it be redefined without it being completely redefined. Could I for example create a function then add or remove a statement from it?
For example say I have this:
def func(x, y): y = 2 * x return yThen could I do something like this:
func() = func() - return ySo then the function would be only:
y = 2 * x
I think an important question here is, _why_ do you want to do this? I agree with King Mir--the example is not very realistic.
So what are you trying to do? Are you just trying to achieve partial reuse of a function? (If that's the case, you're better off just breaking this function into 2 or more, so that you can compose the individual parts for use in other situations.)
