This content originally appeared on DEV Community and was authored by Sabin Sim
Day 5 – Conditional Statements (if / elif / else)
Project: Create a “Smart Login & Grade Evaluator”
01. Learning Goal
By the end of this lesson, you will be able to:
- Understand and use Python conditional statements
- Combine comparison and logical operators in conditions
- Build nested conditions for complex logic
- Create a mini project that checks grades and simulates login
02. Problem Scenario
You are designing a Smart Evaluator App that decides different outcomes:
whether someone is an adult, what their grade is, and whether login credentials are correct.
03. Step 1 – Basic if Statement
A condition executes only when it is True.
age = 20
if age >= 18:
print("You are an adult.")
⚠️ Indentation matters!
Python relies on consistent indentation (recommended: 4 spaces).
04. Step 2 – if ~ else
If the condition is true → run the if block.
If false → run the else block.
age = 15
if age >= 18:
print("Adult")
else:
print("Minor")
05. Step 3 – if ~ elif ~ else
Used for checking multiple conditions in sequence.
Python executes the first True condition only.
score = 85
if score >= 90:
print("Grade A")
elif score >= 80:
print("Grade B")
elif score >= 70:
print("Grade C")
else:
print("Grade F")
06. Step 4 – Nested if (Conditions within Conditions)
You can place one if statement inside another for more complex logic.
age = 20
is_student = True
if age >= 18:
if is_student:
print("Adult student.")
else:
print("Adult but not a student.")
07. Step 5 – Logical Operators in Conditions
You can combine multiple conditions using and, or, not.
temp = 25
if temp > 20 and temp < 30:
print("The weather is warm.")
08. Step 6 – Practice Examples
Example 1: Even or Odd
num = int(input("Enter a number: "))
if num % 2 == 0:
print("Even number.")
else:
print("Odd number.")
Example 2: Age Group Classifier
age = int(input("Enter your age: "))
if age < 13:
print("Child")
elif age < 20:
print("Teenager")
else:
print("Adult")
Example 3: Login Simulation
user_id = input("Enter ID: ")
password = input("Enter password: ")
if user_id == "admin" and password == "1234":
print("Login successful!")
else:
print("Login failed!")
09. Step 7 – Mini Project: Smart Login & Grade Evaluator
Combine multiple conditions into one program that evaluates both login and performance.
user_id = input("Enter ID: ")
password = input("Enter password: ")
if user_id == "admin" and password == "1234":
print("✅ Login successful!")
score = int(input("Enter your score: "))
if score >= 90:
print("Excellent performance! Grade A")
elif score >= 75:
print("Good job! Grade B")
elif score >= 60:
print("You passed. Grade C")
else:
print("Failed. Try again next time.")
else:
print("❌ Invalid credentials. Access denied.")
10. Reflection
You have learned how to:
- Use conditional statements to control program flow
- Combine logical and comparison operators
- Apply nested conditions for complex decisions
- Build a working Smart Evaluator program
In the next lesson, you’ll learn how to repeat actions automatically using loops (for, while) — the foundation of all automation and data processing tasks.
This content originally appeared on DEV Community and was authored by Sabin Sim
Sabin Sim | Sciencx (2025-10-13T21:05:27+00:00) Python basics – Day 05. Retrieved from https://www.scien.cx/2025/10/13/python-basics-day-05/
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