Example-02-11.py

def validate_base_sequence(base_sequence, RNAflag = False):
    """Return True if the string base_sequence contains only upper or lowercase T
    (or U if RNAflag), C, A and G characters, otherwise False"""
    seq = base_sequence.upper()
    return len(seq) == (seq.count('U' if RNAflag else 'T') + 
                        seq.count('C') + 
                        seq.count('A') + 
                        seq.count('G'))

print(validate_base_sequence("AUGC"))