Basic of Python - Variable and Memory Address

 

About this Post

In this post I will be demonstrating how python works using example of variables and their memory addresses.

Explanation with Python Code Examples

#create a variable with value 10

var = 10

#id function is used to get the memory address 

print(id(var)) #1712357776 - memory address

#assign var_new equals to var

var_new = var

#var_new and var are now attached to same memory address

print(id(var_new))#1712357776 - memory address

#reassign value of var 

var = 20

#var gets detached from memory address of 10 and then attached to the memory address of 20 .We can see different memory address now

print(id(var))#1712358096 -memory address

#var_new has old memory address because it is attached to memory address of 10

print(id(var_new))#1712357776 - memory address

print(var) #20

print(var_new) #10

Now rather than reassigning value we will try to update the variable value. For this we can take list / dictionary example. 

# taking a list variable

list_var = [1,2,3,4]

print(id(list_var))#2257786114760 -memory address

#assign list_var_new equals to list_var

list_var_new = list_var

#list_var_new and list_var are now attached to same memory address

print(id(list_var_new))#2257786114760 -memory address

#now instead of reassign ,append an element in list_var

list_var.append(5)

#memory address of list_var will remain same as we are not reassigning it . We are adding one more element in it

print(id(list_var))#2257786114760 -memory address

#memory address of list_var_new is same as list_var

print(id(list_var_new))#2257786114760 -memory address

print(list_var) # [1,2,3,4,5]

#as list_var_new is attached to same memory address as that of list_var, value of list_var_new has updated along with list_var

print(list_var_new) # [1,2,3,4,5]

How to create a copy of variable with different memory address.

For this we will use copy module of python

import copy

list_1 = [1,2,3,4]

list_2 = copy.copy(list_1)

print(id(list_1)) #2257786155784 - memory address

print(id(list_2)) #2257786177544 - memory address

list_1.append(5)

print(id(list_1)) #2257786155784 - memory address

print(id(list_2)) #2257786177544 - memory address

print(list_1) # [1,2,3,4,5]

#value if list_2 won't change now as both variable has different memory address

print(list_2) # [1,2,3,4]