balanced_parenthesis.py

#!/usr/bin/env python3
"""
Statement 

Given an expression string exp, write a program to examine whether 
the pairs and the orders of {,},(,),[,] are correct in exp. 
For example: 
The program should print True for exp = “[()]{}{[()()]()}” and False for exp = “[(])”
"""

OPENING_CHARS = ('{','[','(')
CLOSING_CHARS = ('}', ']', ')')
CHAR_MAP = dict(zip(CLOSING_CHARS, OPENING_CHARS))

def validate_string(string):
    """
    >>> validate_string('[()]{}{[()()]()}')
    True
    >>> validate_string('[(])')
    False
    >>> validate_string('[(]')
    False
    >>> validate_string('{[(())]}{}{}[]{}[()]')
    True
    >>> validate_string('(10*7)+(10−6)')
    True
    """
    stack = []
    try:
        for char in string:
            if char in OPENING_CHARS:
                stack.append(char)
            elif char in CLOSING_CHARS and CHAR_MAP[char] != stack.pop():
                return False
    except IndexError:
        return False
    return len(stack) == 0


def main():
    import doctest
    doctest.testmod()

if __name__ == '__main__':
    main()