"append()"和不带方括号的列表元素之间的区别

Question

指令：get_name_list（）函数返回参数name_list中所有名称的列表，其中给定的字母在参数to_look_for中提供。

问题：如果删除"a_list+=[name]'表达式中"name"的方括号，它将显示以下错误输出。但是，如果使用方括号或"append（）"方法，将生成正确的输出（下面是第二个正确的输出）。我想知道为什么没有[名称]中的方括号，就不能产生正确的输出？

错误输出：

names with d ['J', 'a', 'd', 'e']
names with k ['M', 'i', 'k', 'e', 'y']

错误代码：

def main():
    names = ["Jasper", "Jade", "Mikey", "Giani"]
    names_d = get_name_list(names, "d")
    names_k = get_name_list(names, "k")
    print("names with d", names_d)
    print("names with k", names_k)
    def get_name_list(name_list, to_look_for):
        a_list = [] 
        for name in name_list:
            #print(name)
            if to_look_for in name:
                print(name)
                a_list += name
                #a_list.append(name)
        return a_list
    main()

正确输出：

names with d ['Jade']
names with k ['Mikey']

正确代码：

def main():
    names = ["Jasper", "Jade", "Mikey", "Giani"]
    names_d = get_name_list(names, "d")
    names_k = get_name_list(names, "k")
    print("names with d", names_d)
    print("names with k", names_k)    
def get_name_list(name_list, to_look_for):
    a_list = [] 
    for name in name_list:
        #print(name)
        if to_look_for in name:
            print(name)
            #a_list += name
            a_list.append(name)
    return a_list
main()

Answer 1

'+='运算等于列表内置方法的extend()。它将首先将值更改为列表的等号，然后进行扩展。

在您的情况下：

a_list += name  # which is the same as a_list.extend(name), although name is a string, it will be converted to a list first

将字符串转换为列表时，其作用类似于将'abc'更改为['a', 'b', 'c']。这就是你的['J', 'a', 'd', 'e']来自