Python list和dict方法

Posted 2020-10-26 eddycomeon

###list类的方法


###append 列表内最后增加一个元素
a = [1,2,3,4,5,6,"dssdsd"]
a.append(5)
print(a)

###clear 清空列表内的元素
示例：
a = [1,2,3,4,5,6,"dssdsd"]
a.clear()
print(a)

###copy 复制列表
示例：
a = [1,2,3,4,5,6,"dssdsd"]
v1 = a.copy()
print(v1)

###count 列表内有几个指定的元素个数
示例：
a = [1,2,3,4,5,6,"dssdsd",2]
v1 = a.count(2)
print(v1)

###extend 在列表内最后增加元素
示例：
a = [1,2,3,4,5,6,"dssdsd",2]
v1 = a.extend("4")
print(a)

###index 列表内元素的索引位置
示例：
a = [1,2,3,4,5,6,"dssdsd",2]
v1 = a.index(3)
print(v1)

###index 插入索引插入元素到表内
示例：
a = [1,2,3,4,5,6,"dssdsd",2]
a.insert(2,"index")
print(a)

###pop 利用索引删除指定列表内的元素
示例：
a = [1,2,3,4,5,6,"dssdsd",2]
a.pop(0)
print(a)

###remove 删除列表内指定元素
示例：
a = [1,2,3,4,5,6,"dssdsd",2]
a.remove(1)
print(a)

###reverse 反转列表
示例：
a = [1,2,3,4,5,6,"dssdsd",2]
a.reverse()
print(a)

###sort 列表内从小到大排序 注意只能对数字列表做从小到大排序。
示例：
a = [13,12,23,43,55,6,4545,2]
a.sort()
print(a)


##########dict字典方法

###fromkeys 根据序列创建字典，并指定统一的值
示例：
v = dict.fromkeys(["asd",234,3333,2323],555)
print(v)

###get 打印出字典中key的值
示例：
info = {"k1":3,"k2":4,"k3":5,"k4":6,"k5":7}
v = info.get("k1")  ###get("asd",1111)当一个key asd在字典中不存在时，输出后面的1111
print(v)

###pop 删除字典中一个键值对
示例：
info = {"k1":3,"k2":4,"k3":5,"k4":6,"k5":7}
v = info.pop("k1")
print(info,v)

###popitem 随机删除字典中的一个键值对
示例：
info = {"k1":3,"k2":4,"k3":5,"k4":6,"k5":7}
v = info.popitem()
print(info,v)

###setdefault 设置一个值，当这个key在字典中存在时，获取设置key的值，当设置值不存在时增加到字典中
示例：
info = {"k1":3,"k2":4,"k3":5,"k4":6,"k5":7}
v = info.popitem()
print(info,v)

###update 更新字典中的值，当键值对不存在时，增加到字典中
示例：
info = {"k1":3,"k2":4,"k3":5,"k4":6,"k5":7}
v = info.update({"k1":1000,"k7":4000})
print(info)

###keys 获取字典中所有key的值
示例：
info = {"k1":3,"k2":4,"k3":5,"k4":6,"k5":7}
v = info.keys()
print(v)

###values 获取字典中所有values的值
示例：
info = {"k1":3,"k2":4,"k3":5,"k4":6,"k5":7}
v = info.values()
print(v)