Python列表使用extend添加字符串后，打印最后元素得到字母而非字符串的问题

问题出在list.extend()方法的特性上：它会遍历传入的可迭代对象，将对象中的每个元素逐个添加到列表中。字符串属于可迭代对象，每个字符就是它的元素，所以extend("Motherland")会把"Motherland"拆成单个字符依次加入列表，最后一个元素自然是字符'd'。

有两种简单的修复方式：

方式1：使用append()方法 #

append()会把传入的对象作为单个元素直接添加到列表末尾，完全匹配你的需求：

states_of_america = ["Alabama","Alaska","Arizona","Arkansas","California","Colorado","Connecticut","Delaware","Florida","Georgia","Hawaii","Idaho","Illinois","Indiana","Iowa","Kansas","Kentucky","Louisiana","Maine","Maryland","Massachusetts","Michigan","Minnesota","Mississippi","Missouri","Montana","Nebraska","Nevada","New Hampshire","New Jersey","New Mexico","New York","North Carolina","North Dakota","Ohio","Oklahoma","Oregon","Pennsylvania","Rhode Island","South Carolina","South Dakota","Tennessee","Texas","Utah","Vermont","Virginia","Washington","West Virginia","Wisconsin", "Wyoming"]

states_of_america.append("Motherland")  # 替换extend为append

print(states_of_america[-1])  # 输出：Motherland

方式2：用列表包裹字符串后再extend() #

如果一定要使用extend()，可以把目标字符串放到一个单元素列表中，这样extend()会把这个列表里的唯一元素（完整字符串）加入原列表：

states_of_america = ["Alabama","Alaska","Arizona","Arkansas","California","Colorado","Connecticut","Delaware","Florida","Georgia","Hawaii","Idaho","Illinois","Indiana","Iowa","Kansas","Kentucky","Louisiana","Maine","Maryland","Massachusetts","Michigan","Minnesota","Mississippi","Missouri","Montana","Nebraska","Nevada","New Hampshire","New Jersey","New Mexico","New York","North Carolina","North Dakota","Ohio","Oklahoma","Oregon","Pennsylvania","Rhode Island","South Carolina","South Dakota","Tennessee","Texas","Utah","Vermont","Virginia","Washington","West Virginia","Wisconsin", "Wyoming"]

states_of_america.extend(["Motherland"])  # 把字符串放进列表

print(states_of_america[-1])  # 输出：Motherland

内容的提问来源于stack exchange，提问作者Hriday Valluri