Constants

301.3 Variables and Constants

Variables and Constants — Note 2 of 4

Values that do not change.

What you need to know

A constant is a value that should not change while the program runs. Python has no built-in constant keyword, so by convention we use UPPER_CASE names to signal that a value should not be modified.

What to know

Constants are values that stay the same: VAT_RATE = 0.2
Use ALL_CAPS naming by convention
Python does not enforce constants — it's a convention
Constants make code easier to update and understand

Code examples

Constants convention

python

VAT_RATE = 0.2
MAX_LIVES = 3

price = 50
total = price + (price * VAT_RATE)
print(total)  # 60.0

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Specification notes for programming are in Paper 2.