Mutable vs Immutable Objects in Python

ID and TYPE

''' Example 1 '''
>>> x = "Holberton"
>>> y = "Holberton"
>>> id(x)
140135852055856
>>> id(y)
140135852055856
>>> print(x is y) '''comparing the types'''
True
''' Example 2 '''
>>> a = 50
>>> type(a)
<class: ‘int’>
>>> b = "Holberton"
>>> type(b)
<class: 'string'>

Mutable and Immutable Objects

x = 10x = y
id(x) == id(y)id(y) == id(10)
x = x + 1
id(x) != id(y)id(x) != id(10)
m = list([1, 2, 3])n = m
id(m) == id(n)
m.pop()
id(m) == id(n)
  • Python handles mutable and immutable objects differently.
  • Immutable are quicker to access than mutable objects.
  • Mutable objects are great to use when you need to change the size of the object, example list, dict etc.. Immutables are used when you need to ensure that the object you made will always stay the same.
  • Immutable objects are fundamentally expensive to “change”, because doing so involves creating a copy. Changing mutable objects is cheap.

Exceptions in immutability..

How objects are passed to Functions

def updateList(list1):
list1 += [10]
n = [5, 6]
print(id(n)) # 140312184155336
updateList(n)
print(n) # [5, 6, 10]
print(id(n)) # 140312184155336
def updateNumber(n):
print(id(n))
n += 10
b = 5
print(id(b)) # 10055680
updateNumber(b) # 10055680
print(b) # 5

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