Application: Conversion from Celsius to Fahrenheit

This lesson shows how to write a program that reads a temperature in degrees Celsius and calculates its conversion to degrees Fahrenheit.

Problem statement

Remember that temperatures can be expressed in degrees Celsius (°C) or degrees Fahrenheit (°F). The relationship between these two units of measurement is as follows:

°F = °C⋅1.8 + 32

We want a program that reads a temperature in degrees Celsius and calculates its conversion to degrees Fahrenheit.

Hey!

Think about how to solve the problem before continuing to read!

Solution

The first step to solve any problem is to identify what its inputs are, what its outputs are, and what relationship they have between them. In this case:

• From the problem statement, it is clear that there is an input c which represents a temperature in degrees Celsius.

• Similarly, it is clear that the output is a temperature in degrees Fahrenheit, which can be stored in a real variable named f.

The relationship between the input c and the output f is f = c⋅1.8 + 32.

The solution must therefore perform three tasks, one after the other:

1. Read the value of c. This value must be a real number (with decimals).

2. Calculate the value of f from c. To do this, use the conversion formula.

3. Write the value of f.

In Python, this can be coded as follows:

c = float(input())        # Reading the input
f = c * 1.8 + 32         # Calculating f from c
print(f)                 # Writing the output

The first line assigns to the variable c the value read from the input. The second line assigns to f the appropriate value from c by evaluating the expression c * 1.8 + 32. The third line prints the value of f.

You can try the program here:

If you want to make the program more explicit for the user, you can add a message before reading the temperature in degrees Celsius and another before writing the temperature in degrees Fahrenheit:

c = float(input('Enter the temperature in degrees Celsius:'))
f = c * 1.8 + 32
print('The temperature in degrees Fahrenheit is:', f)

Note that in this application we had to convert the text read with input to a real number with float because the temperature can be a number with decimals. If we had used int instead of float, the program would have given an error if the user had entered a number with decimals.