Python if else and elif for condition check

The code to be executed within if condition is to be indented to create a block of code.

x=10
y=20
if(x>y):
    print("x is greater than y")
else:
    print("y is greater than x")

Output is here

y is greater than x

Python if else and elif to execute code blocks based on condition checking True or False

Using elif

If the first if condition check fails then we can go for for one more check by using elif before using else.
if elif else condition check

x=10
y=20
if(x>y):
    print("x is greaeter than y")
elif(y>15):
    print("y is greater than 15")
    
else:
    print("y is greater than x but less than 15")

Output is here

y is greater than 15

What is the difference between else and elif ?

We don’t check any condition while using else, the code within else block is always executed once the (previous) if condition fails. In case of elif , one more condition is checked.

Avoiding Redundant Checks: Without elif, we might use multiple if statements, which could lead to unnecessary condition checks. For example, if the first condition is True, using elif ensures no further conditions are evaluated. In contrast, using multiple if statements means every condition is evaluated, even if a previous condition has already been met, leading to wasted computation.
Read more how to use elif to get the grade from input mark.

Using Short code

x=10
y=20
if(y>x): print("x is greater than y")

Output is here

x is greater than y

This one is easy.

x=10
y=20
print("y is big") if(y>x) else print("x is big")

One liner if else

mark=45
status='Pass' if mark > 50 else 'Fail'
print(status) # Fail

Write one user defined function to filter odd and even numbers.

def my_check(x):
    return True if x%2==0 else False

Absolute value of input number

i=int(input("input a number "))
if(i<0):i=-i
print("Absolute value is : ",i)

Nested Conditional Statements: Sort three user input numbers

Using logical operators and, or

#n1=int(input('First Number : '))
#n2=int(input('Second Number : '))
#n3=int(input('Third Number : '))
n1=1
n2=2
n3=3
if(n1>=n2 and n1>=n3):
  if(n2>=n3):
    print(n1,n2,n3)
  else:
    print(n1,n3,n2)  
elif(n2>=n1 and n2>=n3):
  if(n1>=n3):
    print(n2,n1,n3)
  else:
    print(n2,n3,n1)  
elif(n3>=n1 and n3>=n2):
  if(n1>=n2):
    print(n3,n1,n2)
  else:
    print(n3,n2,n1)

month='Feb'
if month=='Jan' or month=='Feb' or month=='March':
    print("This is last quarter of the Financial year")
else:
    print("Financial year is not ending now")

Output

This is last quarter of the Financial year

Boolean Logic:

Using and

temperature = 30
is_sunny = True

if temperature > 25 and is_sunny:
    print("It's a hot and sunny day!")
else:
    print("It's not a hot and sunny day.")

Using or

is_weekend = False
is_holiday = True

if is_weekend or is_holiday:
    print("Today is a holiday")
else:
    print("It might be a working day.")

Using not

grade='A'
if not(grade=='A'):
    print("You are not in grade A ")
else:
    print("You are in A grade ")

Output

You are in A grade

Using and , or and not

is_weekend = True
is_holiday = False
weather_is_good = False

if (is_weekend or is_holiday) and not weather_is_good:
    print("It's a perfect day for staying indoors and reading a book.")
else:
    print("Let's go outside and enjoy the day!")

Checking condition inside a loop

for x in range(5,25,5):
  if(x==15):
    break
  print(x)

Output is

5
 10

Handling None value

In Python, None is a special singleton object that often represents the absence of a value. When used in a condition check, such as within an if statement, None is treated as False.

my_variable = None

if my_variable:
    print("The variable has a truthy value.")
else:
    print("The variable is None or otherwise falsy.")

Output

The variable is None or otherwise falsy.

Check Divisibility

i=int(input("Enter any number : "))
if (i%5==0):print("Number is divisible by 5")
else: print("Number is not divisible by 5")

High School Python ( part of Syllabus) View and Download if_else_elif ipynb file ( .html format )

Download the above full source code from Github or run the code in your Google colab platform.

https://github.com/plus2net/Python-basics/blob/main/online_class_if_else_elif_v1.ipynb

Python Basics - if else elif to check condition
19-Feb-2024

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Subhendu Mohapatra

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