Проверка правильности расстановки различных скобок в файле

def isBalanced(file):
    with open(file) as f:
        strInput = f.read()
        if strInput:
            brackets = [ ('(',')'), ('[',']'), ('{','}')]
            kStart = 0
            kEnd = 1
 
            stack = []
 
            for char in strInput:
                for bracketPair in brackets:
                    if char == bracketPair[kStart]:
                        stack.append(char)
                    elif char == bracketPair[kEnd] and len(stack) > 0 and stack.pop() != bracketPair[kStart]:
                        return False
 
            if len(stack) == 0:
                return True
 
        return False

def line_col(symbol,file):
    with open(file) as myFile:
        for num, line in enumerate(myFile, 1):
            if symbol in line:
                idx = line.index(symbol)
                print ('symbol at line:', num,'symol at column:', idx)

class StapleError(Exception):
    def __init__(self, staple, err):
        reason = '%s%s:<<%s>>:%s'
        staple.line = staple.line.replace('\n', '\\n')
        self.reason = reason % (err, staple.idx_line, staple.line, staple.idx_char)
 
    def __str__(self):
        return self.reason
 
 
class Staple:
    def __init__(self, idx_line, line, idx_char):
        self.idx_line = idx_line
        self.line = line
        self.idx_char = idx_char
 
 
def check(filename):
    dstaple = {'(':[], '[':[], '{':[]}
    dstaple_close = {')':'(', ']':'[', '}':'{'}
    
    with open(filename) as f:
        for idx_line, line in enumerate(f, start=1):
            for idx_char, char in enumerate(line, start=1):
                if char in dstaple:
                    dstaple[char].append(Staple(idx_line=idx_line, line=line, idx_char=idx_char))
                elif char in dstaple_close:
                    try:
                        dstaple[dstaple_close[char]].pop()
                    except IndexError:
                        raise StapleError(Staple(idx_line=idx_line, line=line, idx_char=idx_char), 'Error staple close in: ')
    
    for _, l in dstaple.items():
        for staple in l:
            raise StapleError(staple, 'Error staple open in: ')
 
    print('Check is done. File is correct')
 
 
check('file.txt')

def main(filename):
    try: 
        check(filename)
        return True
    except StapleError as e:
        print(e) #debug
        return (e.idx_line, e.idx_char)
 
main('file.txt')