如何在Python的for循环中条件构建列表：合并sequence_C为单列表

你当前代码的核心问题是每次循环都重新初始化了sequence_C为空列表，导致每次循环只能得到一个元素的临时列表并打印。要生成和原sequence结构一致的完整列表，只需调整列表初始化的位置，再统一打印结果即可。

修正后的基础版本代码 #

sequence = ["A","C","G","T","T","A","G","C","T","A","A","C","G"]
sequence_C = []  # 将列表初始化移到循环外部，确保全程复用同一个列表
for i in sequence:
    if i == "A":
        sequence_C.append("T")
    elif i == "T":
        sequence_C.append("A")
    elif i == "C":
        sequence_C.append("G")
    else:
        sequence_C.append("C")
print(sequence_C)  # 循环结束后一次性打印完整列表

更简洁的优化版本 #

可以用字典定义碱基互补映射，再通过列表推导式直接生成结果，代码更紧凑高效：

sequence = ["A","C","G","T","T","A","G","C","T","A","A","C","G"]
base_complement = {"A": "T", "T": "A", "C": "G", "G": "C"}
sequence_C = [base_complement[base] for base in sequence]
print(sequence_C)

内容的提问来源于stack exchange，提问作者Hajar Moukit