Mutable vs Immutable Objects in Python

mutability_in_python.py

"""
    Mutable vs Immutable objects in Python
"""

# Numbers are immutable

a = 10
b = a
b += 1

print(a, b)

# Memory "locations" of numerical values

a = 10
b = a
print(hex(id(a)))
print(id(b))
b = b + 1
print(id(b))

# Strings are immutable too!

s = "I love icecream."
print(s)
print(hex(id(s)))
s = s + " I also like mangoes."
print(s)
print(hex(id(s)))

# Special values are also immutable, but not in the way you think.

a = None
print(hex(id(a)))
a = True
print(hex(id(a)))
a = False
print(hex(id(a)))
a = True
print(hex(id(a)))
a = None
print(hex(id(a)))

# Dictionaries are mutable objects

a = {'name': 'Raj', 'interests': ['computer science', 'music', 'astronomy']}
print(hex(id(a)))
a['age'] = 25
print(a)
print(hex(id(a)))

# Be careful with two names referring to the same mutable object

a = {'a': 1}
b = a
b['a'] = 2
print(a)
print(b)

# Datetime example

import datetime

new_date = datetime.datetime(year=2000, month=1, day=1, hour=0, minute=0, second=0, microsecond=0)
print(new_date)
print(hex(id(new_date)))
new_date = new_date.replace(year=2049)
print(new_date)
print(hex(id(new_date)))