Variables and Simple Values
A variable is a named container for data. Instead of using raw values everywhere, you give them names that explain what they represent. This makes code easier to read, understand, and change.
Creating Variables
To create a variable, choose a name and use the equals sign to assign a value:
name = "Alice"
age = 25
Now name holds the text "Alice" and age holds the number 25. The equals sign here means "store this value" – it's assignment, not a math equation.
Using Variables
Once created, use the variable name anywhere you'd use the value itself:
name = "Alice"
print(name)
print("Hello,", name)
The variable acts as a stand-in for its value. Python looks up what's stored and uses that.
Changing Values
Variables can be reassigned – that's why they're called "variable":
name = "Alice"
print(name)
name = "Bob"
print(name)
After reassignment, the old value is gone. The variable now holds the new value.
Naming Conventions
Good variable names make code self-documenting. Python has conventions:
- Use lowercase letters:
name, notName - Separate words with underscores:
first_name, notfirstName - Be descriptive:
user_ageis clearer thanx - Avoid single letters except for simple counters
# Good names
user_name = "Alice"
total_price = 99.99
is_logged_in = True
# Poor names
x = "Alice"
tp = 99.99
flag = True
Assignment vs Equality
New programmers sometimes confuse = (assignment) with == (equality comparison). They're different operations:
x = 5 # Assignment: store 5 in x
x == 5 # Comparison: is x equal to 5? (returns True or False)
You'll learn more about comparisons when you study conditional logic.
Why Variables Matter
Variables let you write flexible, reusable code. Instead of hardcoding values throughout your program, you define them once and reference them by name. Need to change a value? Update it in one place.
They also make your intentions clear. total_price * tax_rate tells a story that 99.99 * 0.08 doesn't.