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Scope and Lifetime

Scope determines where a name is visible; lifetime determines how long a value exists. Understanding local vs global scope, closures, and lifetime (especially for resources) is important.

x = 10  # global
def f():
    y = 5  # local
    print(x, y)

# Global modification
def g():
    global x
    x = x + 1

# Closure
def make_adder(n):
    def add(x):
        return x + n
    return add
add3 = make_adder(3)
print(add3(4))  # 7

% Globals (use sparingly)
global x
x = 10;

function show()
  global x
  disp(x)
end

% Nested functions capture variables from outer scope
function f = make_adder(n)
  f = @() n + 1; % simple closure example
end

Gotchas

  • Overusing globals leads to fragile code and hard-to-track bugs.
  • Mutable objects referenced in closures can produce surprising results if mutated after closure creation.
  • Resource lifetime: open files/sockets should be closed; prefer context managers (Python with) or onCleanup in Matlab.