Numeric values (int and float behavior) in Python - Mini Project: Build & Apply

Understanding Numeric Values: int and float behavior

📖 Scenario: You are helping a small shop owner calculate prices and discounts. The shop owner needs to understand how whole numbers and decimal numbers work in Python to avoid mistakes in billing.

🎯 Goal: Build a simple Python program that uses integer and float numbers to calculate total price and apply a discount.

📋 What You'll Learn

Create variables with integer and float values

Use a variable to store a discount rate as a float

Calculate the discounted price using numeric operations

Print the final discounted price

💡 Why This Matters

🌍 Real World

Shops and businesses often need to calculate prices with discounts and taxes. Understanding how numbers work helps avoid billing mistakes.

💼 Career

Many programming jobs require handling money and prices correctly, so knowing how integers and floats behave is important.

1

Create initial numeric variables

Create a variable called price and set it to the integer value 100. Create another variable called tax and set it to the float value 7.5.

Python

# Create variables price and tax with values 100 and 7.5
# Your code here

Hint

Remember, integers are whole numbers like 100, and floats are decimal numbers like 7.5.

2

Add a discount rate as a float

Create a variable called discount_rate and set it to the float value 0.1 to represent a 10% discount.

Python

price = 100
tax = 7.5
# Create a variable discount_rate with value 0.1
# Your code here

Hint

Use a decimal number between 0 and 1 to represent the discount rate.

3

Calculate the discounted price

Create a variable called discounted_price that calculates the price after applying the discount rate. Use the formula: price - (price * discount_rate).

Python

price = 100
tax = 7.5
discount_rate = 0.1
# Calculate discounted_price using price and discount_rate
# Your code here

Hint

Multiply price by discount_rate, then subtract from price.

4

Print the discounted price

Write a print statement to display the value of discounted_price.

Python

price = 100
tax = 7.5
discount_rate = 0.1
discounted_price = price - (price * discount_rate)
# Print the discounted_price
# Your code here

Hint

Use print(discounted_price) to show the result.

Practice

1.

Which of the following is an example of a float in Python?

1. 42
2. 3.14
3. -7
4. 0

easy

A. 42

B. 3.14

C. -7

D. 0

Solution

1. Step 1: Understand what a float is

   A float is a number with a decimal point, like 3.14.

2. Step 2: Identify the float among options

   Only 3.14 has a decimal point, so it is a float.

3. Final Answer:

   3.14 -> Option B

4. Quick Check:

   Float = 3.14 [OK]

Hint: Floats always have a decimal point [OK]

Common Mistakes:

• Choosing integers as floats
• Confusing negative numbers with floats
• Ignoring decimal points

2.

Which of the following is the correct way to convert the float 5.7 to an integer in Python?

easy

A. float(5.7)

B. int(5,7)

C. int('5.7')

D. int(5.7)

Solution

1. Step 1: Recall how to convert float to int

   Use the int() function with a float value as argument.

2. Step 2: Check each option

   int(5.7) correctly converts float 5.7 to int 5. int('5.7') causes error, int(5,7) is invalid syntax.

3. Final Answer:

   int(5.7) -> Option D

4. Quick Check:

   int(5.7) = 5 [OK]

Hint: Use int() directly on float to convert [OK]

Common Mistakes:

• Trying int() on string with decimal
• Using wrong syntax like int(5,7)
• Using float() instead of int()

3.

What is the output of the following code?

x = 7 / 2
print(type(x))
print(x)

medium

A. <class 'int'>\n3.5

B. <class 'int'>\n3

C. <class 'float'>\n3.5

D. SyntaxError

Solution

1. Step 1: Understand division operator in Python 3

   Division with / always returns a float, even if numbers divide evenly.

2. Step 2: Evaluate the code

   7 / 2 = 3.5, which is a float. So type(x) is <class 'float'> and x is 3.5.

3. Final Answer:

   <class 'float'>\n3.5 -> Option C

4. Quick Check:

   7 / 2 = 3.5 float [OK]

Hint: Division / always returns float in Python 3 [OK]

Common Mistakes:

• Assuming integer division with /
• Confusing type output format
• Expecting 3 instead of 3.5

4.

Find the error in this code snippet:

num = 4.8
num_int = int(num)
print(num_int + ' is the integer value')

medium

A. Cannot add int and str directly

B. No error, code runs fine

C. Syntax error in print statement

D. Cannot convert float to int

Solution

1. Step 1: Check conversion from float to int

   int(4.8) converts float 4.8 to int 4 without error.

2. Step 2: Check print statement

   Adding int and string directly causes a TypeError in Python.

3. Final Answer:

   Cannot add int and str directly -> Option A

4. Quick Check:

   int + str causes TypeError [OK]

Hint: Convert int to str before adding to string [OK]

Common Mistakes:

• Thinking int() conversion fails
• Ignoring type mismatch in addition
• Assuming print syntax error

5.

You have a list of mixed numbers: nums = [1, 2.5, 3, 4.75, 5]. You want to create a new list with all numbers converted to integers by dropping decimals. Which code correctly does this?

hard

A. new_nums = [int(n) for n in nums]

B. new_nums = [float(n) for n in nums]

C. new_nums = [str(int(n)) for n in nums]

D. new_nums = [round(n) for n in nums]

Solution

1. Step 1: Understand the goal

   We want to convert all numbers to int by dropping decimals, not rounding.

2. Step 2: Evaluate each option

   C uses int() which drops decimals correctly. A converts to string, not int. B converts to float, not int. D rounds numbers, which changes values.

3. Final Answer:

   new_nums = [int(n) for n in nums] -> Option A

4. Quick Check:

   int() drops decimals, list comprehension applies to all [OK]

Hint: Use int() in list comprehension to drop decimals [OK]

Common Mistakes:

• Using round() instead of int()
• Converting to string instead of int
• Using float() which keeps decimals