Scope + parameters

301.12 Subprograms

Subprograms — Note 4 of 4

Local vs global.

What you need to know

Variables defined inside a function are local — they only exist inside that function. Parameters pass data into a function. Global variables exist outside all functions.

What to know

Local variable: created inside a function, dies when function ends
Global variable: created outside, accessible everywhere
Parameters: values passed into a function when called
Avoid using global variables — pass data via parameters instead

Code examples

Scope example

python

def double(n):      # n is a parameter (local)
    result = n * 2  # result is local
    return result

x = 5               # x is global
print(double(x))    # 10
# print(result)     # Error — result doesn't exist here

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Specification notes for programming are in Paper 2.