Mutable object: Object that can be changed after creating it.
Immutable object: Object that cannot be changed after creating it.
In python if you change the value of the immutable object it will create a new object.
Here are the objects in Python that are of mutable type:
list
Dictionary
Set
bytearray
user defined classes
Here are the objects in Python that are of immutable type:
int
float
decimal
complex
bool
string
tuple
range
frozenset
bytes
Questions: Is string an immutable type?
Answer: yes it is, but can you explain this:
Proof 1:
a = "Hello"
a +=" World"
print a
Output
"Hello World"
In the above example the string got once created as "Hello" then changed to "Hello World". This implies that the string is of the mutable type. But it is not when we check its identity to see whether it is of a mutable type or not.
a = "Hello"
identity_a = id(a)
a += " World"
new_identity_a = id(a)
if identity_a != new_identity_a:
print "String is Immutable"
Output
String is Immutable
Proof 2:
a = "Hello World"
a[0] = "M"
Output
TypeError 'str' object does not support item assignment
Questions: Is Tuple an immutable type?
Answer: yes, it is.
Proof 1:
tuple_a = (1,)
tuple_a[0] = (2,)
print a
Output
'tuple' object does not support item assignment