simple python

infix_to_postfix.py

def bi_exp_tree(expstr):
    """ infix to postfix.
    >>> bi_exp_tree("(a+(b*c))")
    'abc*+'
    >>> bi_exp_tree("((a+b)*(z+x))")
    'ab+zx+*'
    >>> bi_exp_tree("((a+t)*((b+(a+c))^(c+d)))")
    'at+bac++cd+^*'
    """
    result = ""
    stack = []
    for c in expstr:
        if c in '(':
            continue
        if c in "+-*/^":
            stack.append(c)
        elif c in ')':
            result += stack.pop()
        else:
            result += str(c)
    return result


if __name__ == '__main__':
    import doctest
    doctest.testmod()