Two functions with the same name in Python

Question

I was just playing around with Python and realized something weird.

I have the below function:

def myfun():    #f1
    return 1
def myfun():    #f2
    return 0

print (myfun())

I changed the values in f1 and f2, but still it always seems to be printing the return value of f2. Is there a specific reason?

I can't understand what you are expecting to happen here, and how that differs from what you actually see. — Daniel Roseman, Feb 25 '15 at 10:05
The issue is obvious for us "scripters", but indeed weird enough for someone with compiled langs background. — georg, Feb 25 '15 at 10:06

score 6 · Accepted Answer · answered Feb 25 '15 at 10:11

In compiled languages you would generally get an error message if you try to define two functions with the same name. But in Python functions are first-class objects and they are defined dynamically.

When you define a new function with the same name as a previously defined function, the function name is now bound to the new function object, and the old function object is reclaimed by the garbage collector.

So what happens to your functions is no different to what happens with the simple integer examples posted in the other answers on this page.

Similarly, we can do the same thing with functions defined using the lambda mechanism. Eg:

>>> myfun=lambda:1; myfun=lambda:0; print(myfun())
0

Is there a way to get an error message? It could be accidental (by mistake) that they have the same name. — Peter Mortensen, Jan 06 '21 at 01:33
OK, I found something: *[How can I detect duplicate method names in a Python class?](https://stackoverflow.com/questions/10761988)* — Peter Mortensen, Jan 06 '21 at 01:47

score 0 · Answer 2 · answered Feb 25 '15 at 09:59

0

Why is that weird? The second function decleration overrides the first, so by the time print is called only f2 exists.

answered Feb 25 '15 at 09:59

WeaselFox

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that's how the interpreter works. suppose you write `a = 10` and then `a = 20` in the next line. What would you expect the value of a to be after those two lines? – WeaselFox Feb 25 '15 at 10:02
I think you should study some oops first ... then it will be more understandable to u – Tushar Gupta Feb 25 '15 at 10:03
@TusharGupta - what is oops? – WeaselFox Feb 25 '15 at 10:04
Object Oriented Programming concepts @WeaselFox :P – Tushar Gupta Feb 25 '15 at 10:05

score 0 · Answer 3 · answered Feb 25 '15 at 10:02

0

The second definition causes the name myfun to be bound to its function replacing the binding produced by the previous definition. This is exactly the same as what happens in:

a = 1
a = 0

print a

answered Feb 25 '15 at 10:02

Dan D.

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weird - the very same example in all three answers. Programmers think alike I guess.. – WeaselFox Feb 25 '15 at 10:03
1

I was also about to post an example using `a`, too. :) – PM 2Ring Feb 25 '15 at 10:04

Two functions with the same name in Python

3 Answers3