Замена в файле символа 0 на символ 1 и наоборот

my_file = open('test.txt')
 
while True:
    line = my_file.readline()
    if not line:
        break
    for i in line:
        if i == '1':
            i = i.replace('1', '0')
        elif i == '0':
            i = i.replace('0', '1')
    print(line)
    with open('test2.txt', 'a') as my_file2:
        my_file2.write(str(line))
 
my_file.close()

my_file = open('test.txt')
 
while True:
    line = my_file.readline()
    if not line:
        break
    for i in line:
        if i == '1':
            line = line.replace('1', '0')
        elif i == '0':
            line = line.replace('0', '1')
    print(line)
    with open('test2.txt', 'a') as my_file2:
        my_file2.write(str(line))
 
my_file.close()

my_file = open('test.txt')
 
while True:
    for_record = []
    line = my_file.readline()
    if not line:
        break
    for i in line:
        if i == '1':
            for_record.append('0')
        elif i == '0':
            for_record.append('1')
        else:
            for_record.append(i)
    print(line)
    with open('test2.txt', 'a') as my_file2:
        my_file2.write(''.join(for_record))
 
my_file.close()

with open('src.txt') as f_open, open('out.txt', 'w') as f_save:
    tmp_for_save = []
    for txt in f_open.readlines():
        for x in txt:
            if x == '1':
                tmp_for_save.append('0')
            elif x == '0':
                tmp_for_save.append('1')
            else:
                tmp_for_save.append(x)
    print(''.join(tmp_for_save), file=f_save)

with open('test.txt') as f:
    text = f.read()
    
text = text.replace('0', '#').replace('1', '0').replace('#', '1')
 
with open('test2.txt', 'w') as f:
    f.write(text)

def select_symbol(txt):
    list_symbol = '~!@#$%^&*+_"/'  # и тд
    for s in list_symbol:
        if s in txt:
            continue
        return s
 
 
with open('src.txt') as f_open, open('test2.txt', 'w') as f_save:
    text = f_open.read()
    symbol = select_symbol(text)
    text = text.replace('0', symbol).replace('1', '0').replace(symbol, '1')
    f_save.write(text)

'\0'

st='012gdg11'
print(''.join(chr(ord(i)^1) if i in '01'else i for i in st ))