Types and Data Structure

Notes

• No primitive types in python
• In python everything is object
• object is an instance of specific class
• There are mutable (list, dict etc) and immutable (str, int) object

Immutable objects

• string instance of str class
• boolean instance of bool class
• integer instance of int class
• decimal number instance of float class
• tuple instance of tuple class
• None instance of NoneType class

Mutable objects

• list instance of list class
• dictionary instance of dict class
• set instance of set class
• user defined class

Variables and objects

variables are simply pointer of location in memory, called id where objects are stored. It means variable contains a reference of the object.

to get the location of object in memory use id() function.

name = 'Kibria'
address_in_memory = id(name)
print(address_in_memory)

It is possible multiple variables refer to the same object in memory. The contain same pointer. So the memory location will be same.

name = 'Kibria'
print(id(name))
# 14036459474849487

name_copy = kibria
print(id(name_copy))
# 14036459474849487

print(id(name) == id(name_copy))
# True

How to check the type of object?

use the type() function.

name = 'Kibria'
print(type(name))
# <class'str'>

age = 41
print(type(age))
# <class 'int'>

How to check the type of class?

print(type(str))
# <class'type'>

print(type(int))
# <class'type'>

print(type(bool))
# <class'type'>

How to check the instance of a class?

name = 'Kibria'
# name is an instance of str
# str is an instance of object

print(isinstance(name, str))
# True

print(isinstance(name, object))
# True

print(isinstance(name, int))
# False

How to see all attributes of a classs or object?

name = 'Kibria'

print(dir(name))
# return a list of all attributes of name