Same function names in python , No error?

Question

To be honest, I was expecting some sort of error, like 'you can't rename two nested functions with same name in a same body like that' , Can we define any number of functions with same name in python ?

In [40]: def add(i,j):
   ....:     def add(i,j):
   ....:         print i+j
   ....:     def add(i,j):    
   ....:         print i-j
   ....:     return add(i,j)
   ....: 

In [41]: add(5,4)
1

Is this Overloading of function, or Overriding of function ??

NO, the last function definition of the same name will override/overwrite all the above definitions — avasal, Jul 18 '12 at 05:27
Rules of overloading specify `The overloaded function must differ either by the arity or data types`, since there are no types of arguments in function definition.. no overloading,,, look at this http://stackoverflow.com/questions/733264/function-overloading-in-python-missing.... — avasal, Jul 18 '12 at 05:39

score 4 · Answer 1 · answered Jul 18 '12 at 05:30

Defining a function is like like assigning a value to a variable. You can do this in Python:

a = 1
a = 2

Likewise you can do this:

def f():
    return 1
def f():
    return 2

In both cases, the last value specified overwrites any previous values. So the last one wins.

The fact that it's a nested function has no bearing on the issue. The same applies in any context.

score 4 · Accepted Answer · edited May 23 '17 at 12:09

Of course. A def statement is functionally an assignment (of the function to the name), and you can have any number of assignments to the same name. (It`s important to realize that function definitions are executed in Python, they are not statically evaluated at compile time.)

There are hacky ways to catch this in class definitions, such as this method I posted in May. If you're using Python 3, there's a better way.

For functions, that won't work, so I believe you're stuck with this behavior.

score 0 · Answer 3 · edited Jul 18 '12 at 13:09

0

the last functions overwrites the others... so, there's no error! :)

edited Jul 18 '12 at 13:09

sloth

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answered Jul 18 '12 at 05:29

trnc

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score 0 · Answer 4 · answered Jul 18 '12 at 06:04

A function definition introduces the function name in the current symbol table. The value of the function name has a type that is recognized by the interpreter as a user-defined function. This value can then be assigned to another name, or even reassigned by redefining the function.

In cases where a function is redefined, the latest definition will be used as it is the one that is recognized by the interpreter.

score 0 · Answer 5 · answered Feb 10 '17 at 15:57

Just to be clear, the second nested add() overwrites the first, but the outer one remains unchanged.

Here is a minimal example:

def do_sth(s):
    def do_sth(s):
        print('Hello, %s!' % s)
    print('Ola')
    do_sth(s)

>>> do_sth('chuinul')
Ola
Hello, chuinul!
>>> do_sth('chuinul')
Ola
Hello, chuinul!

When you call do_sth() the second time, this is still the outer function you defined that is being called. Otherwise you would have only had:

>>> do_sth('chuinul')
Hello, chuinul!

Same function names in python , No error?

5 Answers5