如何检查字符串中的特定字符？

Question

当我运行程序时,它总是打印为true.例如,如果我输入AAJJ,它将打印为true,因为只检查第一个字母是否为真.有人能指出我正确的方向吗？谢谢!

squence_str = raw_input("Enter either A DNA, Protein or RNA sequence:")

def DnaCheck():

    for i in (squence_str):
        if string.upper(i) =="A":
            return True
        elif string.upper(i) == "T":
            return True
        elif string.upper(i) == "C":
            return True
        elif string.upper(i) == "G":
            return True
        else:
            return False

print "DNA ", DnaCheck()

Answer 1

您需要检查DNA序列中的所有碱基是否有效.

def DnaCheck(sequence):
    return all(base.upper() in ('A', 'C', 'T', 'G') for base in sequence)