C++ to Python

Question

In c++ we use pointers for reference to variables in function parameters, but in Python there is no concept of Pointers. So how can we implement the two choices of functional calls i.e. call by value and call by reference in Python.

Answer 1

In python, all objects are transfered by reference. However, some objects are immuable, and their modification implies the creation of a modified copy of the object. Any user-defined data-type is by default considered as mutable.

You can use the ctypes library, that contains a real pointer datatype but... I'm not sure it is a good way.

If you want to simulate pointers, on basic types, you could do wrappers around native objects :
class Wrapper:
def __init__(self, value):
self.value = value

But there is no real way to have pointers in Python.

Answer 2

Lists act as a pointer. Use list for call by reference and normal variable passing for call by value.

Sure lists do take a lot of memory but it'll help you.

e.g.
def func(a):
a[0] += 1

a = [5]
func(a)
print(a[0])

Link to code for your reference: https://code.sololearn.com/cc1A5NDY3Svw/#py

Answer 3

Milind Yadav it is not a matter of 'normal variable' or 'list'. It is a matter of mutability, as I explained previously. And you're actually saying the same thing as I said : creating a wrapper object around another object.

Answer 4

Yep.. that's true.... unfortunately there is no other way....this was just a short code.... that's why I mentioned this

Answer 5

We are using the OOPS concept to overcome this problem

Answer 6

J Santhosh Kumar But OOP is also available in c++, I don't think that can be used here. Please read the question again.

Answer 7

Yeah but In python there is no pointers. They using only OOPS concept.

Answer 8

Yes, I'd loved to see pointers too... But at the end, I never really needed them in Python.