Why conditional statements are needed in Python - See It in Action

Why conditional statements are needed

📖 Scenario: Imagine you are creating a simple program that helps decide what to wear based on the weather. Sometimes it is sunny, sometimes rainy, and sometimes cold. You want the program to give different advice depending on the weather.

🎯 Goal: You will build a small program that uses conditional statements to give clothing advice based on the weather condition.

📋 What You'll Learn

Create a variable called weather with the exact value 'sunny'.

Create a variable called advice and set it to an empty string.

Use an if statement to check if weather is 'sunny' and set advice to 'Wear sunglasses.'.

Use an elif statement to check if weather is 'rainy' and set advice to 'Take an umbrella.'.

Use an else statement to set advice to 'Wear a jacket.'.

Print the advice variable.

💡 Why This Matters

🌍 Real World

Conditional statements are used in many real-life programs like weather apps, games, and websites to make decisions based on user input or data.

💼 Career

Understanding how to use conditional statements is a basic skill for any programming job because it helps you control the flow of your program.

1

Create the weather variable

Create a variable called weather and set it to the string 'sunny'.

Python

# Create the variable weather with value 'sunny'
# Your code here

Hint

Use the equals sign = to assign the value 'sunny' to the variable weather.

2

Create the advice variable

Create a variable called advice and set it to an empty string ''.

Python

weather = 'sunny'
# Create the variable advice as an empty string
# Your code here

Hint

Set advice to '' to start with no advice.

3

Add conditional statements for weather

Use an if statement to check if weather is 'sunny' and set advice to 'Wear sunglasses.'. Then use an elif statement to check if weather is 'rainy' and set advice to 'Take an umbrella.'. Finally, use an else statement to set advice to 'Wear a jacket.'.

Python

weather = 'sunny'
advice = ''
# Use if, elif, else to set advice based on weather
# Your code here

Hint

Use if, elif, and else to check the weather and set the advice.

4

Print the advice

Write a print statement to display the value of the advice variable.

Python

weather = 'sunny'
advice = ''
if weather == 'sunny':
    advice = 'Wear sunglasses.'
elif weather == 'rainy':
    advice = 'Take an umbrella.'
else:
    advice = 'Wear a jacket.'
# Print the advice
# Your code here

Hint

Use print(advice) to show the advice on the screen.

Practice

1. Why do we use conditional statements like if in Python?

easy

A. To repeat code multiple times

B. To store multiple values in a list

C. To make decisions and run code only when certain conditions are true

D. To define a function

Solution

1. Step 1: Understand the purpose of conditional statements

   Conditional statements check if something is true or false to decide what code to run.

2. Step 2: Compare with other options

   Repeating code is done by loops, storing values is done by lists, and defining functions uses def.

3. Final Answer:

   To make decisions and run code only when certain conditions are true -> Option C

4. Quick Check:

   Conditional statements = decision making [OK]

Hint: Think: 'Should I run this code or not?' [OK]

Common Mistakes:

• Confusing conditionals with loops
• Thinking conditionals store data
• Mixing conditionals with function definitions

2. Which of the following is the correct syntax for a simple if statement in Python?

easy

A. if x > 5: print('Yes')

B. if x > 5 print('Yes')

C. if (x > 5) { print('Yes') }

D. if x > 5 then print('Yes')

Solution

1. Step 1: Recall Python if syntax

   Python uses a colon (:) after the condition and indentation for the code block.

2. Step 2: Check each option

   if x > 5: print('Yes') uses colon and correct syntax; others use wrong keywords or braces not used in Python.

3. Final Answer:

   if x > 5: print('Yes') -> Option A

4. Quick Check:

   Colon and indentation = correct if syntax [OK]

Hint: Remember: Python uses ':' after condition [OK]

Common Mistakes:

• Using 'then' keyword (not in Python)
• Using braces {} like other languages
• Omitting colon after condition

3. What will be the output of this code?

age = 18
if age >= 18:
    print('Adult')
else:
    print('Child')

medium

A. Adult

B. No output

C. Child

D. Error

Solution

1. Step 1: Check the condition age >= 18

   Since age is 18, the condition is true.

2. Step 2: Determine which block runs

   The if block runs and prints 'Adult'. The else block is skipped.

3. Final Answer:

   Adult -> Option A

4. Quick Check:

   Condition true = 'Adult' printed [OK]

Hint: Check if condition is true or false [OK]

Common Mistakes:

• Assuming else block runs when condition is true
• Confusing >= with >
• Thinking no output if condition is true

4. Find the error in this code:

number = 10
if number > 5
    print('Big number')

medium

A. Indentation error in print statement

B. Missing colon ':' after the if condition

C. Wrong comparison operator

D. Variable 'number' is not defined

Solution

1. Step 1: Check the if statement syntax

   Python requires a colon ':' at the end of the if condition line.

2. Step 2: Identify the missing colon

   The code misses ':' after if number > 5, causing a syntax error.

3. Final Answer:

   Missing colon ':' after the if condition -> Option B

4. Quick Check:

   Colon missing after if condition [OK]

Hint: Always put ':' after if condition [OK]

Common Mistakes:

• Forgetting colon after if
• Misaligning indentation
• Changing comparison operator unnecessarily

5. You want to print 'Good morning' if the hour is less than 12, 'Good afternoon' if hour is between 12 and 18 (inclusive), and 'Good evening' otherwise. Which code correctly uses conditional statements?

hard

A. if hour < 12:
print('Good morning')
elif hour > 12 and hour < 18:
print('Good afternoon')
else:
print('Good evening')

B. if hour < 12:
print('Good morning')
if 12 <= hour <= 18:
print('Good afternoon')
else:
print('Good evening')

C. if hour < 12:
print('Good morning')
else if 12 <= hour <= 18:
print('Good afternoon')
else:
print('Good evening')

D. if hour < 12:
print('Good morning')
elif 12 <= hour <= 18:
print('Good afternoon')
else:
print('Good evening')

Solution

1. Step 1: Check correct use of if, elif, and else

   if hour < 12: print('Good morning') elif 12 <= hour <= 18: print('Good afternoon') else: print('Good evening') uses elif correctly and covers all hour ranges without overlap.

2. Step 2: Identify errors in other options

   if hour < 12: print('Good morning') if 12 <= hour <= 18: print('Good afternoon') else: print('Good evening') uses two separate if statements causing multiple prints; if hour < 12: print('Good morning') else if 12 <= hour <= 18: print('Good afternoon') else: print('Good evening') uses invalid 'else if' syntax; if hour < 12: print('Good morning') elif hour > 12 and hour < 18: print('Good afternoon') else: print('Good evening') misses equality for 12 and 18 in afternoon range.

3. Final Answer:

   Code with proper if, elif, and else and correct ranges -> Option D

4. Quick Check:

   Use elif for multiple conditions [OK]

Hint: Use elif for multiple exclusive conditions [OK]

Common Mistakes:

• Using 'else if' instead of 'elif'
• Using multiple separate if causing multiple outputs
• Incorrect range checks missing equal signs