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Python Programs - Functions

Function to calculate BMI and categorize - Python Program

Example 1 :

Python 
def bmi(weight, height):
    """Calculate BMI and return category."""
    value = weight / (height ** 2)
    if value < 18.5:
        category = "Underweight"
    elif value < 24.9:
        category = "Normal"
    elif value < 29.9:
        category = "Overweight"
    else:
        category = "Obese"
    return value, category

bmi_value, category = bmi(70, 1.75)
print("BMI:", round(bmi_value, 2), category)

Output

 
OUTPUT  :
BMI: 22.86 Normal

Example 2 : Advanced Program

Python 
def calculate_bmi_and_categorize(weight_kg, height_m):
    """
    Calculates BMI and categorizes it based on standard classifications.

    Args:
        weight_kg (float): Weight in kilograms.
        height_m (float): Height in meters.

    Returns:
        tuple: A tuple containing the calculated BMI (float) and its category (str).
               Returns (None, "Invalid input") if height_m is zero or negative.
    """
    if height_m <= 0:
        return None, "Invalid input: Height must be a positive value."

    bmi = weight_kg / (height_m ** 2)

    if bmi < 18.5:
        category = "Underweight"
    elif 18.5 <= bmi < 24.9:
        category = "Normal weight"
    elif 24.9 <= bmi < 29.9:
        category = "Overweight"
    else:
        category = "Obese"

    return bmi, category

# Example Usage:
weight = int(input("Enter Weight in Kilograms (kg) : "))  # kilograms
height = float(input("Enter Height in Metres (m) : ")) # meters

bmi_value, bmi_category = calculate_bmi_and_categorize(weight, height)

if bmi_value is not None:
    print(f"For a weight of {weight} kg and height of {height} m:")
    print(f"Your BMI is: {bmi_value:.2f}")
    print(f"Category: {bmi_category}")
else:
    print(bmi_category)

# Another example:
weight_invalid = 60
height_invalid = 0
bmi_value_invalid, bmi_category_invalid = calculate_bmi_and_categorize(weight_invalid, height_invalid)
print(bmi_category_invalid)

Output

 
OUTPUT  :
Enter Weight in Kilograms (kg) : 75
Enter Height in Metres (m) : 1.75
For a weight of 75 kg and height of 1.75 m:
Your BMI is: 24.49
Category: Normal weight
Invalid input: Height must be a positive value.

Explanation:

The calculate_bmi_and_categorize function takes two arguments: weight_kg (in kilograms) and height_m (in meters).

Input Validation:

It first checks if height_m is valid (greater than zero) to prevent division by zero or negative values, returning an "Invalid input" message if necessary.

BMI Calculation:

It calculates the BMI using the formula: BMI = weight / (height^2).

Categorization:

It then categorizes the calculated BMI into one of the following standard classifications: "Underweight", "Normal weight", "Overweight", or "Obese" using a series of if-elif-else statements.

Return Value:

The function returns a tuple containing the calculated bmi and its corresponding category.

 

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