Python列表的常用方法(增删改查)

# 列表的常用方法
# 插入
# 删除
# 清空
# 统计元素个数

# 1.查找某元素在列表内的下标索引
mylist = ["it", "xj",  "xiaoji", "python"]
index = mylist.index("it")
print(index)

# 2.如果被查找的元素不存在会报错
# mylist = ["it", "xj",  "xiaoji", "python"]
# index = mylist.index("hello")
# print(index)

# 3.修改特定下标索引的值
mylist = ["it", "xj",  "xiaoji", "python"]
mylist[2] = 'xj'
print(mylist)

# 4.在指定下标位置插入新元素
mylist = ["it", "xj",  "xiaoji", "python"]
mylist.insert(1, "23")  # 参数一:插入的下标,参数二:插入的数据
print(mylist)

# 5.在列表的尾部追加```单个```新元素
mylist = ["it", "xj",  "xiaoji", "python"]
mylist.append("一批")
print(mylist)

# 6.在列表的尾部追加```一批```新元素
mylist = ["it", "xj",  "xiaoji", "python"]
mylist.extend([4, 5, 6])  # 参数为数据容器
print(mylist)

# 7.删除指定下标索引的元素(2种方式)
# 7.1方式一:del 列表[下标]
mylist = ["it", "xj",  "xiaoji", "python"]
del mylist[0]
print(mylist)

# 7.2方式二:列表.pop(下标),这个方法是取出内容
mylist = ["it", "xj",  "xiaoji", "python"]
num = mylist.pop(0)
print(f"通过pop方法取出0号下标后列表内容为:{mylist},取出的元素是{num}")

# 8.删除某元素在列表中的第一个匹配项
mylist = ["it", "xj",  "xiaoji", "python"]
mylist.remove("xj")
print(mylist)

# 9.清空列表
mylist = ["it", "xj",  "xiaoji", "python"]
mylist.clear()
print(mylist)

# 10.统计列表内某元素的数量
mylist = ["it", "xj", "xj", "xiaoji", "python"]
count = mylist.count("xj")
print(count)

# 11.统计列表中全部的元素数量
mylist = ["it", "xj",  "xiaoji", "python"]
count = len(mylist)
print(count)

1.   0
2.   ['it', 'xj', 'xj', 'python']
3.   ['it', '23', 'xj', 'xiaoji', 'python']
4.   ['it', 'xj', 'xiaoji', 'python', '一批']
5.   ['it', 'xj', 'xiaoji', 'python', 4, 5, 6]
6.   ['xj', 'xiaoji', 'python']
7.   通过pop方法取出0号下标后列表内容为:['xj', 'xiaoji', 'python'],取出的元素是it
8.   ['it', 'xiaoji', 'python']
9.   []
10.  2
11.  4