Parameter passing and return values in Python

Parameter passing in Python is similar to Java, with its own memory-recycling mechanism, which differs greatly from C + +.

1. Parameter passing of the function:

>>> a = [123]>>> def Fun (a):        for in  A:            print I
        A.append (4)>>> fun (a)12344807792> >> a[1234]

As you can see from the above results, Python's function passing is a reference pass, so modifying the object content inside the function causes the object content to change outside the function.

This is not true for some built-in types, such as int,float.

Note that if you do a del operation within a function for a passed in parameter, it will not affect the actual object, because del deletes the reference, and the actual object has a reference count of at least 1, so it will not be recycled.

2. Return of function:

>>> def Fun ():        = [123]        print ID (a)        return  a>>> a = Fun ()44806192>>> ID (a)44806192 

>>> def Fun ():        1        Print ID (a)        return  a>> > A = Fun ()34243104>>> ID (a)34243104

As you can see, the function returns a reference to the object, and the object now has a reference count of 1, so it is not reclaimed by memory.

This is definitely a mistake in C + +, but Python has its own memory-recycling mechanism, so it's no problem.

3. Summary:

Python is similar to Java in that there is no pointer to an object, and each object is manipulated by reference, so that when the function is passed and the function returns, the action on the same object is implemented by a reference to the same object. When the function call ends, the memory of the object does not disappear, but the reference itself is recycled.

Parameter passing and return values in Python