Add two numbers in Python (with and without input)

The program asks for two numbers, adds them with + and prints the sum. The one step that beginners often miss is converting the typed text into numbers first.

The program

python

first = float(input("Enter the first number: "))
second = float(input("Enter the second number: "))

total = first + second

print(f"{first} + {second} = {total}")

Typed in this example: 12.5, 7.25. Press Run to type your own.

output

Enter the first number: 12.5
Enter the second number: 7.25
12.5 + 7.25 = 19.75

How it works

input() always gives back a string, even when the user types digits.
float(...) turns that string into a number that can have a decimal point.
+ on two numbers adds them. The f-string puts the three values into one line.

Why you must convert

+ on two strings does not add them. It joins them end to end:

python

a = "12"
b = "30"

print(a + b)
print(int(a) + int(b))

output

1230
42

int or float

Use int() when the user must type whole numbers. Then 7 prints as 7 and not 7.0:

python

first = int(input("First whole number: "))
second = int(input("Second whole number: "))
print("Sum:", first + second)

Typed in this example: 25, 17. Press Run to type your own.

output

First whole number: 25
Second whole number: 17
Sum: 42

int("7.5") raises a ValueError, so use float() if decimals are allowed. The type conversion page shows what each conversion accepts.

Without input

If the numbers are already in your code, add them directly. sum() adds every number in a list:

python

a = 15
b = 27
print("Sum:", a + b)

print(sum([3, 4.5, 10]))
print(0.1 + 0.2)
print(round(0.1 + 0.2, 2))

output

Sum: 42
17.5
0.30000000000000004
0.3

The last two lines show a normal property of floats: most decimal fractions cannot be stored exactly in binary, so a tiny error can appear. Use round() or an f-string such as f"{total:.2f}" when you print the result.