Fundamentals of Conditional Logic Review
TL;DR
Conditional logic lets your programs make decisions by executing different code blocks based on whether a statement is true or false. It's the cornerstone of dynamic behavior, allowing your software to respond intelligently to various inputs and situations. Mastering conditionals is essential for building any useful and interactive application.
1. The Mental Model
Think of conditional logic as asking "if this, then that." You're giving your program a specific question to evaluate, and based on the answer (true or false), it follows a different path. It's like a fork in the road for your code.
2. The Core Material
What is a Condition?
A condition is a statement that can only be evaluated as either true or false. These are often called Boolean expressions. You use comparison operators to create these conditions.
== (equal to): Is x equal to y?
!= (not equal to): Is x not equal to y?
> (greater than): Is x greater than y?
< (less than): Is x less than y?
>= (greater than or equal to): Is x greater than or equal to y?
<= (less than or equal to): Is x less than or equal to y?
Basic if Statements
The simplest conditional structure, an if statement executes a block of code only if its condition is true.
score = 85
if score >= 70:
print("You passed the exam!")
if-else Statements
When you want to execute one block of code if a condition is true and a different block if it's false, you use an if-else statement.
temperature = 22
if temperature > 25:
print("It's hot outside!")
else:
print("It's not too hot.")
if-elif-else Statements (Chained Conditionals)
For multiple possible conditions, you use elif (short for "else if"). The program checks conditions in order, executing the first code block whose condition is true, then skipping the rest. The else block acts as a catch-all if none of the preceding if or elif conditions are met.
grade = 88
if grade >= 90:
print("You got an A!")
elif grade >= 80:
print("You got a B!")
elif grade >= 70:
print("You got a C.")
else:
print("You need to study more.")
Logical Operators
You can combine multiple conditions using logical operators:
and: Both conditions must be true.
or: At least one condition must be true.
not: Reverses the truth value of a conditio