Python密码子转氨基酸程序elif条件不生效 仅输出Phe_

所有分支的条件判断写法错误，是程序输出异常的核心原因：
Python的or运算符会对两侧表达式独立计算布尔值，你写的if(codon_sequence[i]=="UUU" or "UUC" or "TTT" or "TTC")并不会判断密码子是否匹配四个值中的任意一个，实际执行逻辑是先算codon_sequence[i] == "UUU"的布尔结果，再依次和后面的字符串"UUC"、"TTT"、"TTC"做或运算。
而Python中非空字符串的布尔值恒为True，所以不管第一个等式判断结果是什么，只要走到or "UUC"这一步，整个if条件的结果就固定为True，程序永远会进入第一个分支输出Phe_，后续所有elif分支根本没有执行机会。

不要用冗长的or拼接判断，直接用in关键字判断密码子是否在对应氨基酸的密码子元组里，写法简洁还不会出错。修复后的完整代码如下：

codon_sequence = []
print("Enter no. of codons you want")
n = int(input())
for i in range(n):
    codon = str(input()).strip() # 过滤输入时误带的首尾空格
    codon_sequence.append(codon)
print(codon_sequence)

# 直接遍历列表元素比通过索引访问更简洁
for codon in codon_sequence:
    if codon in ("UUU", "UUC", "TTT", "TTC"):
        print("Phe_")
    elif codon in ("UUA", "UUG", "CUU", "CUC", "CUG", "CUA", "TTA", "TTG", "CTT", "CTC", "CTG", "CTA"):
        print("Leu_")
    elif codon in ("UCU", "UCC", "UCG", "UCA", "AGU", "AGC", "TCT", "TCC", "TCG", "TCA", "AGT", "AGC"):
        print("Ser_")
    elif codon in ("UAU", "UAC", "TAT", "TAC"):
        print("Tyr_")
    elif codon in ("UGU", "UGC", "TGT", "TGC"):
        print("Cys_")
    elif codon in ("UGG", "TGG"):
        print("Trp_")
    elif codon in ("CCU", "CCC", "CCA", "CCG", "CCT"):
        print("Pro_")
    elif codon in ("CGU", "CGC", "CGA", "CGG", "AGA", "AGG", "CGT"):
        print("Arg_")
    elif codon in ("CAU", "CAC", "CAT"):
        print("His_")
    elif codon in ("CAA", "CAG"):
        print("Gln_")
    elif codon in ("AUU", "AUC", "AUA", "ATT", "ATC", "ATA"):
        print("Ile_")
    elif codon == "AUG":
        print("Met_")
    elif codon in ("ACU", "ACC", "ACA", "ACG", "ACT"):
        print("Thr_")
    elif codon in ("GUU", "GUC", "GUA", "GUG", "GTT", "GTC", "GTA", "GTG"):
        print("Val_")
    elif codon in ("GCU", "GCC", "GCA", "GCG", "GCT"):
        print("Ala_")
    elif codon in ("GGU", "GGC", "GGA", "GGG", "GGT"):
        print("Gly_")
    elif codon in ("GAU", "GAC", "GAT"):
        print("Asp_")
    elif codon in ("GAA", "GAG"):
        print("Glu_")
    elif codon in ("AAU", "AAC", "AAT"):
        print("Asn_")
    elif codon in ("AAA", "AAG"):
        print("Lys_")
    else:
        print("Stop_")

内容的提问来源于stack exchange，提问作者saptarshi