Variables
- Variables are used to store data.
- Variables are like containers.
- Variables are case sensitive.
- Variables are dynamically typed.
- Variables are assigned using
=operator. - Variables are assigned using
camelCaseorsnake_caseorPascalCaseorUPPERCASEorlowercase.
Syntax
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# variable_name = value
name = "Irfan"
age = 20
Example
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name = "Irfan"
age = 20
print(name)
print(age)
Rules
- Variable name can contain
a-z,A-Z,0-9,_. - Variable name can’t start with number.
- Variable name can’t contain special characters like
!,@,#,$,%,^,&,*,(,),-,+,=,{,},[,],\,|,:,;,",',<,>,,,.,?,/. - Variable name can’t be reserved keyword.
- Variable name can’t be same as function name.
- Variable name can’t be same as class name.
- Variable name can’t be same as module name.
- Variable name can’t be same as package name.
- Variable name can’t be same as method name.
- Variable name can’t be same as instance name.
- Variable name can’t be same as exception name.
Example
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# Valid Variable Name
name = "Irfan"
age = 20
_name = "Irfan"
_name_ = "Irfan"
name_ = "Irfan"
Name = "Irfan"
NAME = "Irfan"
Name_ = "Irfan"
NAME_ = "Irfan"
_name1 = "Irfan"
_name_1 = "Irfan"
_name1_ = "Irfan"
# Invalid Variable Name
1name = "Irfan"
name@ = "Irfan"
name! = "Irfan"
name# = "Irfan"
name$ = "Irfan"
name% = "Irfan"
name^ = "Irfan"
name& = "Irfan"
name* = "Irfan"
Naming Convention
- Variable name should be meaningful.
- Variable name should be short.
- Variable name should be descriptive.
- Variable name should be readable.
- Variable name should be understandable.
Example
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# Bad Naming Convention
a = "Irfan"
b = 20
print(a)
print(b)
# Good Naming Convention
name = "Irfan"
age = 20
print(name)
print(age)
type() Function
- type() function is used to get type of variable.
- It returns type of the variable
Syntax
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type(variable_name)
<class ‘str’>
Example
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name = "Irfan"
print(type(name))
# <class 'str'>
age = 20
print(type(age))
# <class 'int'>
height = 5.8
print(type(height))
# <class 'float'>
Variable Types
- String
- Integer
- Float
- Boolean
- Complex
- List
- Tuple
- Set
- Dictionary
- None
- Bytes
- Bytearray
- Range
- Frozenset
- Ellipsis
- NotImplemented
- Module
- Class
- Function
- Method
Example
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# String
name = "Irfan"
print(name)
# Integer
age = 20
print(age)
# Float
height = 5.8
# Boolean
is_voter = True
# Complex
complex_number = 2 + 3j
# List
list_of_numbers = [1, 2, 3, 4, 5]
# Tuple
tuple_of_numbers = (1, 2, 3, 4, 5)
# Set
set_of_numbers = {1, 2, 3, 4, 5}
# Dictionary
dictionary_of_numbers = {1: "One", 2: "Two", 3: "Three", 4: "Four", 5: "Five"}
# None
nothing = None
# Bytes
bytes_of_numbers = b"12345"
# Bytearray
bytearray_of_numbers = bytearray(12345)
# Range
range_of_numbers = range(1, 6)
# Frozenset
frozenset_of_numbers = frozenset({1, 2, 3, 4, 5})
# Ellipsis
ellipsis = ...
# NotImplemented
not_implemented = NotImplemented
# Module
import random
import math
# Class
class Person:
pass
# Function
def add(a, b):
return a + b
# Method
class Person:
def __init__(self, name, age):
self.name = name
self.age = age
def get_name(self):
return self.name
def get_age(self):
return self.age
Assigning Multiple Variables
- Assigning multiple variables at once.
Syntax
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variable_name1, variable_name2, variable_name3 = value1, value2, value3
Example
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name, age, height = "Irfan", 20, 5.8
print(name, age, height)
Assigning Same Value to Multiple Variables
- Assigning same value to multiple variables at once.
Syntax
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variable_name1 = variable_name2 = variable_name3 = value
Example
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name = age = height = "Irfan"
print(name, age, height)
Swapping Variables
- Swapping values of two variables.
Syntax
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variable_name1, variable_name2 = variable_name2, variable_name1
Example
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age, name = 20, "Irfan"
print("Before Swapping")
print("Age:", age)
print("Name:", name)
age, name = name, age
print("After Swapping")
print("Age:", age)
print("Name:", name)
Addition of variables
- Addition of two variables.
Syntax
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variable_name1 + variable_name2
Example
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# Integer Addition
a = 10
b = 20
c = a + b
print(c)
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# String Addition
a = "Mohd"
b = "Irfan"
c = a + b
print(c)
# MohdIrfan
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# String and Integer Addition
a = "Mohd"
b = 20
print(a + b)
# Error: TypeError: can only concatenate str (not "int") to str
TypeError: can only concatenate str (not “int”) to str
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# Integer and Float Addition
a = 10
b = 20.5
print(a + b)
# 30.5
Typecasting :
To convert string to integer use int() function
- str()
- int()
- float()
- list()
- dict()
- tuple()
Example
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# String to Integer
a = "10"
b = int(a)
print(b)
# 10
# string + integer
val1 = "54"
val2 = "32"
print(int(val1) + int(val2))
# 86
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# string + integer
my = "I have "
count = 100
subscribe = " subscribers"
print(my + str(count) + subscribe)
# I have 100 subscribers