Python Program to Find Largest of Two Numbers

You can find the largest of two numbers in Python using max(a, b) or by comparing with if a > b and printing the larger one.

Examples

Inputa = 5, b = 10

Output10

Inputa = -3, b = -7

Output-3

Inputa = 4, b = 4

Output4

How to Think About It

To find the largest of two numbers, think about comparing them directly. If one number is bigger than the other, that number is the largest. If they are equal, either number is the largest.

Algorithm

1

Get the first number as input.

2

Get the second number as input.

3

Compare the two numbers using greater than operator.

4

If the first number is greater, select it as the largest.

5

Otherwise, select the second number as the largest.

6

Print the largest number.

Code

python

a = float(input("Enter first number: "))
b = float(input("Enter second number: "))

if a > b:
    largest = a
else:
    largest = b

print("The largest number is", largest)

Output

Enter first number: 5
Enter second number: 10
The largest number is 10

Dry Run

Let's trace the example where a = 5 and b = 10 through the code

1

Input numbers

a = 5, b = 10

2

Compare a and b

Is 5 > 10? No

3

Select largest

Since 5 is not greater, largest = 10

4

Print result

Output: The largest number is 10

Step	a	b	Condition (a > b)	Largest
1	5	10	False	10

Why This Works

Step 1: Input numbers

We take two numbers from the user using input() and convert them to floats for general use.

Step 2: Compare numbers

Using if a > b, we check which number is bigger.

Step 3: Print largest

We store the larger number in largest and print it to show the result.

Alternative Approaches

Using max() function

python

a = float(input("Enter first number: "))
b = float(input("Enter second number: "))
largest = max(a, b)
print("The largest number is", largest)

This is shorter and uses Python's built-in function for clarity and simplicity.

Using ternary operator

python

a = float(input("Enter first number: "))
b = float(input("Enter second number: "))
largest = a if a > b else b
print("The largest number is", largest)

This method uses a compact one-line conditional expression for assignment.

Complexity: O(1) time, O(1) space

Time Complexity

The program compares two numbers once, so it runs in constant time, O(1).

Space Complexity

Only a few variables are used, so space complexity is constant, O(1).

Which Approach is Fastest?

All approaches run in constant time; using max() is most readable and concise.

Approach	Time	Space	Best For
If-else comparison	O(1)	O(1)	Clear logic and step-by-step understanding
max() function	O(1)	O(1)	Simplicity and readability
Ternary operator	O(1)	O(1)	Compact code style