python中如何给列表添加元素

>>> a = ["aa","bb","cc"]  ## 创建列表
>>> a
['aa', 'bb', 'cc']
>>> a.append("dd")  ## append添加
>>> a
['aa', 'bb', 'cc', 'dd']
>>> a.extend(["ee"])
>>> a
['aa', 'bb', 'cc', 'dd', 'ee']
>>> a.extend(["ff","gg"])   ## extend同时添加多个元素
>>> a
['aa', 'bb', 'cc', 'dd', 'ee', 'ff', 'gg']
>>> a.insert(2,"xxxx")  ## insert添加
>>> a
['aa', 'bb', 'xxxx', 'cc', 'dd', 'ee', 'ff', 'gg']

>>> a = ["aa","bb"]
>>> b = ["xx","yy"]
>>> a + b
['aa', 'bb', 'xx', 'yy']