from itertools import cycle, islice

def caesarCipher(s, k):
    if k == 0: return s
        
    # shift alphabet
    alpha = string.ascii_lowercase
    shifted = list(islice(cycle(alpha),
                          k, k+len(alpha)
                          ))
    
    s_shift = []
    for char in s:
        # uppercase flag
        upper = False
        if char.isupper():
            upper = True
            char = char.lower()
            
        # handling non-letters
        match = re.match(r'\W', char)
        if match or char.isnumeric() or char == '_':
            s_shift.append(char)
            
        # cipher
        else:
            idx = alpha.index(char)
            new_char = str(shifted[idx])
            if upper: new_char = new_char.upper()
            s_shift.append(new_char)
						
    return str(''.join(s_shift))