'''
A bracket is considered to be any one of the following characters: (, ), {, }, [, or ].
Two brackets are considered to be a matched pair if the an opening bracket (i.e., (, [, or {) occurs to the left of a closing bracket (i.e., ), ], or }) of the exact same type. There are three types of matched pairs of brackets: [], {}, and ().
A matching pair of brackets is not balanced if the set of brackets it encloses are not matched. For example, {[(])} is not balanced because the contents in between { and } are not balanced. The pair of square brackets encloses a single, unbalanced opening bracket, (, and the pair of parentheses encloses a single, unbalanced closing square bracket, ].
By this logic, we say a sequence of brackets is balanced if the following conditions are met:
It contains no unmatched brackets.
The subset of brackets enclosed within the confines of a matched pair of brackets is also a matched pair of brackets.
Given  strings of brackets, determine whether each sequence of brackets is balanced. If a string is balanced, return YES. Otherwise, return NO.
Function Description
Complete the function isBalanced in the editor below. It must return a string: YES if the sequence is balanced or NO if it is not.
isBalanced has the following parameter(s):
s: a string of brackets
Input Format
The first line contains a single integer , the number of strings. 
Each of the next  lines contains a single string , a sequence of brackets.
Constraints

, where  is the length of the sequence.
All chracters in the sequences ∈ { {, }, (, ), [, ] }.
Output Format
For each string, return YES or NO.
'''

def balanced(phrase):
    new_str = ''
    for item in phrase:
        if item in '[({)}]':
            new_str = new_str + item
    
    if new_str[-1] in '[{(' or new_str[0] in '}])':
        return 'NO'
   
    i = 0
    while i < len(new_str):
        print 
        if (new_str[i] == '}' and new_str[i-1] == '{') or (new_str[i] == ')' and new_str[i-1] == '(') or (new_str[i] == ']' and  new_str[i-1] == '['): 
          new_str = new_str[:i-1] + new_str[i+1:] 
          i -=1
        else:
            i += 1
    if len(new_str) == 0:
        return 'YES'
    else:
        return 'NO'
        
print balanced('{[()]}')