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Conditionals

Conditionals let programs choose different actions depending on values or conditions. They are the foundation of branching logic: if a condition holds, do something; else do something else.

Conditionals use boolean expressions (see the Comparisons lesson) and short-circuiting logic.

# Simple if
score = 75
if score >= 60:
    print("pass")

# if / else
x = 7
if x % 2 == 0:
    print("even")
else:
    print("odd")

# if / elif / else chain
n = -1
if n < 0:
    print("negative")
elif n == 0:
    print("zero")
else:
    print("positive")

# Truthiness
items = []
if items:
    print("has items")
else:
    print("empty")

# Ternary expression
result = "yes" if score > 50 else "no"

% Simple if
score = 75;
if score >= 60
  disp('pass')
end

% if / else
x = 7;
if mod(x,2) == 0
  disp('even')
else
  disp('odd')
end

% if / elseif / else
n = -1;
if n < 0
  disp('negative')
elseif n == 0
  disp('zero')
else
  disp('positive')
end

% Check for empty arrays
A = [];
if ~isempty(A)
  disp('has items')
else
  disp('empty')
end

Gotchas

  • Python uses indentation to delimit blocks; Matlab uses end. Mixing styles causes syntax errors.
  • In Matlab = is assignment and == is comparison; accidentally using = in a conditional will error or assign.
  • Truthiness: empty containers are Falsey in Python, and isempty is the usual check in Matlab.
  • Order matters in elif/elseif chains — the first matching branch runs.