Master Python Variables and Data Types: A Complete Beginner’s Guide

Variable Storage and Assignment

Variables are stored in memory; creating a variable allocates space. Python assigns values without type declarations. The equals sign (=) assigns the value on the right to the variable name on the left. A variable must be assigned before use.

#!/usr/bin/python
# -*- coding: UTF-8 -*-
counter = 100  # integer
miles = 1000.0  # float
name = "John"  # string
print counter
print miles
print name

Multiple assignment is supported:

a = b = c = 1
a, b, c = 1, 2, "john"

Standard Data Types

Python defines five standard data types: Numbers, Strings, Lists, Tuples, Dictionaries.

Numbers

Numbers are immutable; assigning creates a new object. Python supports int, long, float, complex. Examples:

int: 10, 100, -786, 0x69

long: 51924361L, -0x19323L, 0122L

float: 0.0, 15.20, -21.9, 32.3+e18

complex: 3.14j, 45.j, 9.322e-36j

Objects can be deleted with the del statement, e.g., del var or del var_a, var_b.

Strings

Strings are sequences of characters. They can be indexed from left (0) or right (-1). Slicing s[ start : end ] extracts substrings. Concatenation uses +, repetition uses *.

s = "ilovepython"
print s[1:5]  # love

Lists

Lists are mutable ordered collections, defined with brackets []. They support indexing, slicing, concatenation (+) and repetition (*).

mylist = ["runoob", 786, 2.23, "john", 70.2]
print mylist[0]          # runoob
print mylist[1:3]        # [786, 2.23]

Tuples

Tuples are immutable ordered collections, defined with parentheses (). They cannot be reassigned.

mytuple = ("runoob", 786, 2.23, "john", 70.2)
print mytuple[0]          # runoob

Dictionaries

Dictionaries are unordered key‑value mappings, defined with braces {}. Keys are used for access.

person = {"dept": "sales", "code": 6734, "name": "john"}
print person["name"]      # john

Data Type Conversion

Built‑in functions convert between types, returning new objects. Common functions include int(), long(), float(), complex(), str(), repr(), eval(), tuple(), list(), set(), dict(), chr(), ord(), hex(), oct().