while — Advanced Examples

Starts a loop that repeats as long as its condition is true

EasyIntermediateAdvancedExpert

While for state machines

Using while loops to implement state-based logic.

python
def tokenize(expression):
    tokens = []
    i = 0
    while i < len(expression):
        ch = expression[i]
        if ch.isspace():
            i += 1
        elif ch.isdigit():
            num = ""
            while i < len(expression) and expression[i].isdigit():
                num += expression[i]
                i += 1
            tokens.append(("NUM", int(num)))
        elif ch in "+-*/":
            tokens.append(("OP", ch))
            i += 1
        else:
            i += 1
    return tokens

result = tokenize("12 + 34 * 5")
for token in result:
    print(token)

while loops are natural for parsers and state machines where the number of iterations depends on the input content, not just its length.

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