Function evaluate

data_structures/stacks/prefix_evaluation.py:26–55

Evaluate a given expression in prefix notation. Asserts that the given expression is valid. >>> evaluate("+ 9 * 2 6") 21 >>> evaluate("/ * 10 2 + 4 1 ") 4.0 >>> evaluate("2") 2 >>> evaluate("+ * 2 3 / 8 4") 8.0

(expression)

def evaluate(expression):
    """
    Evaluate a given expression in prefix notation.
    Asserts that the given expression is valid.

    >>> evaluate("+ 9 * 2 6")
    21
    >>> evaluate("/ * 10 2 + 4 1 ")
    4.0
    >>> evaluate("2")
    2
    >>> evaluate("+ * 2 3 / 8 4")
    8.0
    """
    stack = []

    # iterate over the string in reverse order
    for c in expression.split()[::-1]:
        # push operand to stack
        if is_operand(c):
            stack.append(int(c))

        else:
            # pop values from stack can calculate the result
            # push the result onto the stack again
            o1 = stack.pop()
            o2 = stack.pop()
            stack.append(operators[c](o1, o2))

    return stack.pop()


def evaluate_recursive(expression: list[str]):