Passing Argument By Object Reference

Passing argument by object reference, you will not understand in coding level it more of memory thing how memory work for passing an argument I will give you two example from python and C.

Python (Object Reference)

def change_box(box):
    box["item"] = "new toy"  

my_box = {"item": "old toy"}  
print("Before:", my_box)  # Output: {'item': 'old toy'}
change_box(my_box)  # Pass the reference to the box
print("After:", my_box)  # Output: {'item': 'new toy'}

Before: {'item': 'old toy'}
After: {'item': 'new toy'}

1. Creating my_box:

• Python creates a dictionary {"item": "old toy"} at some memory address, say 0x1234.
• my_box is a variable that holds the reference 0x1234 (the address of the dictionary).

1. Calling change_box(my_box):

• The function change_box gets a copy of the reference 0x1234, stored in its parameter box.
• Now, both my_box (outside) and box (inside the function) point to the same dictionary at 0x1234.

3.Modifying the Object:

• When box["item"] = "new toy" runs, it modifies the dictionary at 0x1234.
• Since my_box still points to 0x1234, it sees the change ({"item": "new toy"}).

1. What If We Reassign? (Uncomment the line):

• If you uncomment box = {"item": "another box"}, Python creates a new dictionary at a different address, say 0x5678.
• Now, box points to 0x5678, but my_box still points to 0x1234. The original dictionary (my_box) remains unchanged.

C (Pass by Value)

#include 

void try_to_change(int x) {
    x = 100;  
}

int main() {
    int num = 10;
    try_to_change(num);
    printf("num = %d\n", num);  
    return 0;
}

num = 10

num is stored at some memory address, say 0x1000, with value 10. The function try_to_change gets a copy of num’s value (x = 10) stored at a different address, say 0x2000. Changing x only affects 0x2000, not 0x1000.

• Passing by Reference Using Pointers

#include 

void change_number(int *ptr) {
    *ptr = 100;  
}

int main() {
    int num = 10;
    printf("Before: num = %d\n", num);  
    change_number(&num);  // Pass the address of num
    printf("After: num = %d\n", num);   
    return 0;
}

Before: num = 10
After: num = 100

I know this topic is complicated, not easy to understand. But please do let me know which part you don't understand. This is easiest way to understand.