def f(seq):
    for i in range(len(seq)):
        seq = seq[1:] + seq[:1]
        yield seq
print(''.join(list(f('xy'))))

class MyExc(Exception): pass 
def f():
    raise MyExc()
    return  'f'
try:
    print(f())
    print('try')
except MyExc:
    print('exc')

x = 0
try:
    1/0
    x += 1
except ZeroDivisionError:
    x += 1
else: 
    x += 1
    1/0
    x += 1
print(x)

try:
    print('try')
    1/0
    
else:
    print('else')

x = 0
try:
    x += 1
except ZeroDivisionError:
    x += 1
else: 
    x += 1
    1/0
    x += 1
print(x)

d = {'a': 1, 'b': 2, 'c': 3}
x = [string for string, digit in d.items() if digit > 1]
print(x)

sum([1 << i for i in range(5)])

x = 0
try:
    x += 1
    try: 
        x += 1
        1/0
    except ZeroDivisionError:
        x += 1
except ZeroDivisionError:
    x += 1
else: 
    x += 1
print(x)

def f(*seqs):
    seqs = [list(s) for s in seqs]
    while all(seqs):
        yield tuple(s.pop (0) for s in seqs)
s1, s2 = 'ab', '123'
print(list(f(s1, s2)))

class A:
    def message(self):
        print('1', end='') 
        
    def __enter__(self):
        print('2', end='') 
        return self
    
    def __exit__(self, exc_type, exc_value, exc_tb):
        if exc_type is None:
            print('3', end='')  
        else:
            print ('4', end='')
            return True   
        
with A() as action:
    action.message()