How to create a weight converter using if and else statements

Overview

A weight converter is simply used to convert between different units of mass such as: kilogram (kg), stones (st), grams (g), pounds (lbs) etc.

In this shot, we are going to create a weight converter to help us convert and determine the weight of a user be it in kilogram (kg) or in pounds (lbs).

The relationship between kilograms and pounds is given as:
1 kg = 2.205 lbs

This simply means that for every value given in kilogram that we want to convert to pounds, we simply multiply the number by 2.205. Also for any value of pounds we want to convert to kilogram, we simply divide the number by 2.205.

Example

If a user weighs 70kg and wants to know the equivalence in pounds (lbs):

Solution

70kg is converted to pounds as: 70 × 2.205 = 154.35 lb

It is as simple as that!

Writing the program

Now let’s write a program that dynamically converts a unit in kilogram to pounds and vice-versa.

Code

try:
    weight = int(input('What is your weight? '))
    unit = input('In (kg) or (lb)? ')
    if unit.lower() == "kg":
        conversion = weight * 2.205
        print(f'Your weight in pounds is {conversion}lb')
    else:
        conversion = weight // 2.205
        print(f'your weight in kilograms is {conversion}kg')
except ValueError:
    print('Sorry you made an invalid input')

Output 1

What is your weight? 95
In (kg) or (lb)? KG
Your weight in pounds is 209.475lb

Output 2

What is your weight? 209
In (kg) or (lb)? lb
Your weight in kilograms is 94.0kg

Output 3

What is your weight? kg
Sorry you made an invalid input

Explanation

• Line 1: We create a try and except block to handle any ValueError.
• Line 2: We define a variable weight where the user gives an input of their weight.
• Line 3: We define another variable unit where we ask the user to input the unit of the weight (whether kg or lb) they inputted in line 2.
• Line 4: Using an if statement, we state a condition that if the user gave a value equal to kg, and also in any letter case not minding, the return value should continue in line 4.
• Line 5: Here we define a variable conversion to help compute the conversion and proceed with the condition given in line 4.
• Line 6: We return the output of the first condition given in line 4.
• Line 7: Using an else statement, we state a second condition that if the user gave another input other than that in line 4, the return value should continue in line 8.
• Line 8: Here we re-define the variable conversion to help compute and proceed with the condition given in line 10.
• Line 9: We return the output of the second condition in line 7.
• Line 10: We complete the try and except block which helps to check for any ValueError.
• Line 11: We return an output to let the user know that they just made a ValueError.