MASTER YOUR LOGIC BUILDING:Phase 1 - Level 1: Simple Conditions

Mastering phase 1 - level 1: simple conditions concepts and implementation.

Phase 1 - Level 1: Simple Conditions

Why This Matters

Imagine you're at a movie theater. The ticket checker looks at your age and decides: "You're 18 or older — go in. Otherwise, you need a parent." That's conditional thinking — making a decision based on a yes/no question.

Programs do the same thing. They look at a value, ask a question, and choose what to do next. This is one of the most important skills in programming, and you're about to learn it from scratch.

What You'll Learn

  • How to write if and else statements
  • How to compare values using relational operators
  • How to check if a number is positive, negative, even, or odd
  • How to read a problem and turn it into a simple decision

Comparison Operators (Your Yes/No Tools)

These operators compare two values and give you True or False:

OperatorMeaningExample
`>`greater than`5 > 3` → True
`<`less than`2 < 10` → True
`==`equal to`7 == 7` → True
`!=`not equal to`4 != 5` → True
`>=`greater or equal`5 >= 5` → True
`<=`less or equal`3 <= 8` → True
Tip: Use == (two equals signs) to check equality. A single = is for assigning a value, not comparing.

Your First If-Else

Here's the basic shape every decision follows:

if condition:
    # runs when condition is True
    print("Yes!")
else:
    # runs when condition is False
    print("No.")

Step-by-step: First, think about the question ("Is the number positive?"). Then write the condition (num > 0). Finally, write what to print in each case.

Example: Is a number even?

num = int(input("Enter a number: "))

if num % 2 == 0:
    print("Even")
else:
    print("Odd")

How to think about it:

  1. "Even" means divisible by 2 with no remainder
  2. num % 2 gives the remainder when divided by 2
  3. If remainder is 0 → even; otherwise → odd

Three outcomes? Use elif

When you have more than two paths (like positive, negative, or zero):

if num > 0:
    print("Positive")
elif num < 0:
    print("Negative")
else:
    print("Zero")

Python checks from top to bottom and stops at the first match.

Common Mistakes

  • Forgetting the colon after if, elif, or else — Python needs it!
  • Wrong indentation — code inside if must be indented (usually 4 spaces)
  • Using `=` instead of `==` — if num = 5 is an error; use if num == 5
  • Comparing strings and numbers — "5" == 5 is False; make sure types match

Tips

  • Say the question out loud before writing code: "If the number is greater than zero, print Positive."
  • Start with the simplest case, then add elif and else
  • Test with easy numbers first: 0, 1, -1, a big even number, a big odd number

Practice Focus

Scroll down to the hands-on examples below. Try each one yourself before reading the solution. Focus on:

  • Turning a plain-English question into an if condition
  • Using % to check divisibility (even/odd, divisible by 5)
  • Handling two or three possible outcomes confidently

Hands-on Examples

Check if Number is Positive, Negative, or Zero

# Take a number as input
num = float(input("Enter a number: "))

# Check if positive, negative, or zero
if num > 0:
    print("Positive")
elif num < 0:
    print("Negative")
else:
    print("Zero")

We use if-elif-else to check three conditions: greater than 0 (positive), less than 0 (negative), or exactly 0.

Progress
Next: Phase 1 - Level 2: Nested If & Multiple Conditions

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