Balanced delimiters with a stack

Problem

Implement is_balanced(text) for (), [], and {}. Ignore non-delimiter characters.

Starter code

def is_balanced(text):
    pass

Reveal answer or reference solution

def is_balanced(text):
    pairs = {')': '(', ']': '[', '}': '{'}
    stack = []
    for ch in text:
        if ch in '([{':
            stack.append(ch)
        elif ch in pairs:
            if not stack or stack.pop() != pairs[ch]:
                return False
    return not stack

Public tests

is_balanced('a[(b+c)*{d-e}]') → True
is_balanced('([)]') → False
is_balanced('(()') → False

Local history

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