Is it possible to change a function's default parameters in Python?

Question

In Python, is it possible to redefine the default parameters of a function at runtime?

I defined a function with 3 parameters here:

def multiplyNumbers(x,y,z):
    return x*y*z

print(multiplyNumbers(x=2,y=3,z=3))

Next, I tried (unsuccessfully) to set the default parameter value for y, and then I tried calling the function without the parameter y:

multiplyNumbers.y = 2;
print(multiplyNumbers(x=3, z=3))

But the following error was produced, since the default value of y was not set correctly:

TypeError: multiplyNumbers() missing 1 required positional argument: 'y'

Is it possible to redefine the default parameters of a function at runtime, as I'm attempting to do here?

Answer 1

Just use functools.partial

 multiplyNumbers = functools.partial(multiplyNumbers, y = 42)

One problem here: you will not be able to call it as multiplyNumbers(5, 7, 9); you should manually say y=7

If you need to remove default arguments I see two ways:

1. Store original function somewhere

   oldF = f
   f = functools.partial(f, y = 42)
   //work with changed f
   f = oldF //restore
   

2. use partial.func

   f = f.func //go to previous version.