Lesson 4.1: Comparison Operators

What Are Comparison Operators?

Comparison operators let you compare two values and get a Boolean result — either True or False. They are the foundation of decision-making in Python. Every time your program needs to choose what to do, it starts with a comparison.

Think of comparisons as asking yes-or-no questions:

• "Is this number bigger than 10?" → True or False
• "Are these two words the same?" → True or False
• "Is the user old enough?" → True or False

# Simple comparisons
print(5 > 3)
print(10 == 10)
print("hello" == "world")

The Six Comparison Operators

Python provides six comparison operators. Here they all are:

age = 18

print("Is adult:", age >= 18)
print("Is teenager:", age >= 13 and age <= 19)
print("Is child:", age < 13)

# More examples with variables
x = 10
y = 20

print(x == y)    # False - 10 is not equal to 20
print(x != y)    # True  - 10 is not equal to 20
print(x < y)     # True  - 10 is less than 20
print(x > y)     # False - 10 is not greater than 20
print(x <= 10)   # True  - 10 is less than or equal to 10
print(x >= 15)   # False - 10 is not greater than or equal to 15

== vs = (A Very Common Mistake!)

One of the most common beginner mistakes is confusing = (assignment) with == (comparison). They look similar but do very different things:

# = is for assignment (storing a value)
score = 95         # Put 95 into the variable score

# == is for comparison (checking equality)
print(score == 95)  # Ask: "Is score equal to 95?"
print(score == 100) # Ask: "Is score equal to 100?"

If you accidentally use = where you meant ==, Python will often give you a SyntaxError. This is actually helpful — it catches the mistake for you!

# This would cause a SyntaxError:
# if score = 95:   # WRONG - this is assignment, not comparison
# if score == 95:  # CORRECT - this is comparison

Comparing Strings

You can compare strings too! Python compares strings character by character using their Unicode values (essentially alphabetical order, with some rules).

# String equality
name = "Alice"
print(name == "Alice")    # True
print(name == "alice")    # False - case matters!
print(name != "Bob")      # True

# Case-insensitive comparison
user_input = "YES"
print(user_input.lower() == "yes")  # True

# Alphabetical comparison
print("apple" < "banana")    # True - 'a' comes before 'b'
print("cat" < "dog")       # True - 'c' comes before 'd'
print("zebra" > "apple")   # True - 'z' comes after 'a'

When comparing strings, uppercase letters come before lowercase letters. This means "Z" < "a" is True!

# Uppercase vs lowercase ordering
print("Z" < "a")    # True - uppercase letters come first
print("A" < "a")    # True
print(ord("A"))      # 65 - Unicode value of 'A'
print(ord("a"))      # 97 - Unicode value of 'a'

Comparing Different Types

Python allows comparing integers and floats (they work as you would expect), but comparing unrelated types like strings and numbers may give unexpected results or errors.

# Comparing int and float works fine
print(5 == 5.0)      # True - same value
print(3 < 3.5)       # True
print(10.0 >= 10)    # True

# Comparing string and int with == returns False
print("5" == 5)      # False - different types!

# Comparing string and int with < causes an error
# print("5" < 5)      # TypeError!

# If the user types "18", input() gives you the STRING "18"
age_str = "18"         # This is what input() returns

# This won't work as expected:
print(age_str >= 18)    # TypeError!

# Convert to int first:
age = int(age_str)
print(age >= 18)        # True - now it works!

Storing Comparison Results

Since comparisons return True or False, you can store the result in a variable. This is useful for making your code more readable.

# Store comparison results in variables
temperature = 35

is_hot = temperature > 30
is_freezing = temperature <= 0

print("Is it hot?", is_hot)
print("Is it freezing?", is_freezing)

# You can use these variables later in if statements
# (you'll learn about if statements in the next lesson!)

# Practical example: checking a password
stored_password = "python123"
entered_password = "Python123"

passwords_match = stored_password == entered_password
print("Access granted:", passwords_match)