Easy
Python
Guide
Conditional Statements
Conditional statements are fundamental building blocks in Python programming that allow your code to make decisions based on different circumstances. Think of them as the "if-then" logic that humans use every day - if it's raining, then take an umbrella. In Python, these statements use keywords like if, elif (else if), and else to control which parts of your code execute depending on whether certain conditions are true or false. The basic syntax involves writing if followed by a condition, then a colon, with the code to execute indented on the following lines.
The most common conditional statements start with a simple if statement. For example, if temperature > 25: might trigger code that turns on air conditioning. You can extend this logic with elif to check multiple conditions in sequence, such as elif temperature < 10: to turn on heating instead. Finally, else acts as a catch-all for any situation not covered by the previous conditions. The conditions themselves often use comparison operators like == (equals), != (not equals), > (greater than), < (less than), and logical operators like and, or, and not to create more complex decision-making logic.
In web development roles, conditional statements are everywhere. A web developer might use them to check if a user is logged in before displaying certain content, or to validate form data before processing it. For instance, if user.is_authenticated: could show a personalised dashboard, whilst else: might redirect to a login page. E-commerce sites rely heavily on conditionals to apply discounts, check stock levels, or determine shipping costs based on location and item weight. These statements ensure that users see relevant content and that the website behaves appropriately under different circumstances.
Data analysts and scientists use conditional statements extensively for data cleaning and analysis. They might write if pd.isna(value): to handle missing data points, or use conditions to categorise data into groups. For example, a marketing analyst could use conditionals to segment customers based on spending habits: if total_spent > 1000: assigns them to a "premium" category. Financial analysts use these statements to flag unusual transactions, calculate different tax rates based on income brackets, or trigger alerts when certain market conditions are met.
In automation and systems administration, conditional statements are crucial for creating robust, self-managing systems. A system administrator might write scripts that check disk space and send alerts when storage is running low, or automatically restart services if they stop responding. DevOps engineers use conditionals in deployment scripts to handle different environments - perhaps if environment == 'production': uses different database settings than development. Even simple task automation, like organising files based on their extensions or processing emails based on their sender, relies heavily on conditional logic to make intelligent decisions about how to handle different scenarios.
Syndax
Some examples of where conditional statements are used:
# Example 1: User authentication in a web application
user_role = "admin"
if user_role == "admin":
print("Access granted to admin panel")
elif user_role == "moderator":
print("Access granted to moderation tools")
else:
print("Standard user access only")
# Example 2: E-commerce discount calculation
order_total = 150.00
customer_type = "premium"
if customer_type == "premium" and order_total > 100:
discount = 0.15 # 15% discount
elif order_total > 200:
discount = 0.10 # 10% discount for large orders
elif order_total > 50:
discount = 0.05 # 5% discount for medium orders
else:
discount = 0 # No discount
final_price = order_total * (1 - discount)
print(f"Final price: £{final_price:.2f}")
# Example 3: Temperature control system
current_temp = 18
target_temp = 22
if current_temp < target_temp - 2:
print("Heating system ON")
elif current_temp > target_temp + 2:
print("Cooling system ON")
else:
print("Temperature maintained")
# Example 4: Data validation for user registration
email = "user@example.com"
password = "SecurePass123"
age = 17
if "@" not in email or "." not in email:
print("Invalid email address")
elif len(password) < 8:
print("Password must be at least 8 characters")
elif age < 18:
print("Must be 18 or older to register")
else:
print("Registration successful")
# Example 5: File processing based on extension
filename = "report.pdf"
if filename.endswith('.pdf'):
print("Processing PDF document")
elif filename.endswith('.xlsx') or filename.endswith('.csv'):
print("Processing spreadsheet data")
elif filename.endswith('.jpg') or filename.endswith('.png'):
print("Processing image file")
else:
print("Unsupported file type")
# Example 6: Database connection with error handling
connection_status = "failed"
retry_count = 3
if connection_status == "connected":
print("Database ready for queries")
elif connection_status == "failed" and retry_count > 0:
print(f"Retrying connection... {retry_count} attempts remaining")
else:
print("Connection failed - switching to offline mode")
# Example 7: Employee salary calculation with overtime
hours_worked = 45
hourly_rate = 15.50
is_weekend = True
if hours_worked > 40:
regular_pay = 40 * hourly_rate
overtime_hours = hours_worked - 40
overtime_rate = hourly_rate * 1.5
overtime_pay = overtime_hours * overtime_rate
total_pay = regular_pay + overtime_pay
else:
total_pay = hours_worked * hourly_rate
if is_weekend:
total_pay += 50 # Weekend bonus
print(f"Total pay: £{total_pay:.2f}")
# Example 8: System monitoring alert levels
cpu_usage = 85
memory_usage = 92
disk_space = 15 # percentage free
if cpu_usage > 90 or memory_usage > 95 or disk_space < 10:
alert_level = "CRITICAL"
elif cpu_usage > 80 or memory_usage > 85 or disk_space < 20:
alert_level = "WARNING"
else:
alert_level = "NORMAL"
print(f"System status: {alert_level}")
# Example 9: Game scoring system
player_score = 8500
lives_remaining = 2
level = 5
if player_score > 10000:
rank = "Master"
elif player_score > 5000 and level >= 3:
rank = "Expert"
elif player_score > 1000:
rank = "Intermediate"
else:
rank = "Beginner"
if lives_remaining == 0:
print(f"Game Over! Final rank: {rank}")
else:
print(f"Current rank: {rank}, Lives: {lives_remaining}")
# Example 10: Network security access control
ip_address = "192.168.1.100"
time_of_day = 14 # 24-hour format
security_clearance = "high"
allowed_ips = ["192.168.1.100", "192.168.1.101", "10.0.0.5"]
if ip_address not in allowed_ips:
print("Access denied: Unauthorised IP address")
elif time_of_day < 9 or time_of_day > 17:
if security_clearance != "high":
print("Access denied: Outside business hours")
else:
print("After-hours access granted for high clearance")
else:
print("Access granted")