Balanced Brackets

Code editors check this on every keystroke. Write is_balanced(text) that returns True when the round (), square [] and curly {} brackets in text are balanced, and False otherwise.

Balanced means every closing bracket matches the most recent opening bracket that is still open, and nothing is left open at the end. Every other character is ignored.

Examples

is_balanced("{[()()]}")               # returns True
is_balanced("([)]")                   # returns False
is_balanced("print(len([1, 2, 3]))")  # returns True
is_balanced("((")                     # returns False

In "([)]" the ] arrives while the ( is still open, so the brackets close in the wrong order.

Note

A string with no brackets at all, including the empty string, is balanced.