一、列表功能及方法
1,建立列表,列表的元素可以包含任何数数据类型,可以是数字,字符串,列表,元组,字典,集合和布尔值
li = [1, 12, 9, "age", ["石振文", ["19", 10], "庞麦郎"], "alex", True] # 通过list类创建的对象,li
列表list在Python中其实就是一个类,赋值后就是调用这个类的一个对象,list.xx()就是对象的方法,也可称之为参数。
2,列表的在后面添加元素,方法为append()
1 li = [11, 22, 33, 22, 44]
2 li.append(5)
3 li.append("alex")
4 li.append([1234,2323])
5 print(li)
2 清空列表
li.clear()
print(li)
3 拷贝,浅拷贝
v = li.copy()
print(v)
4. 计算元素出现的次数
v = li.count(22)
print(v)
5. 扩展原列表,参数:可迭代对象,方法为extend()会把一个可迭代的对象,迭代出来作为元素加入到列表中,也就是替我们用For循环逐个加入到列表。
li = [11, 22, 33, 22, 44]
li.append([9898,"不得了"])
print(li)
输出结果为:
[11, 22, 33, 22, 44, [77, 99]]
>>> li = [11, 22, 33, 22, 44]
>>> li.index(22)
1 只查到第一个元素22所在的索引位置
[11, 22, 33, 22, 44, 9898, '不得了']
>>> li = [11, 22, 33, 22, 44]
>>>
>>> li.extend(234) #如果输入的对象是不可迭代的,它会报错。
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'int' object is not iterable
它与append的差别在于,append会把整个输入对象作为一个元素加入到列表的后面。
6. 根据值获取当前值索引位置(左边优先)方法为index(xx)
>>> li = [11, 22, 33, 22, 44]
>>> li.append([77,99])
>>> print(li)
[11, 22, 33, 22, 44, [77, 99]]
7. 在指定索引位置插入元素 ,方法为insert()
>>> li = [11, 22, 33, 22, 44]
>>> li.insert(0,99) #指定在第一个位置插入99
>>> print(li)
[99, 11, 22, 33, 22, 44]
>>> li.insert(2,99) #指定在第三个位置插入99
>>> print(li)
[99, 11, 99, 22, 33, 22, 44]
8、 删除某个值(1.指定索引;2. 默认最后一个),并获取删除的值
li = [11, 22, 33, 22, 44]
v = li.pop()
print(li)
[11, 22, 33, 22]
print(v)
44
li = [11, 22, 33, 22, 44]
v = li.pop(1)
print(li)
[22, 33, 22, 44]
print(v)
11
9. 删除列表中的指定值,左边优先 方法remove()
li = [11, 22, 33, 22, 44]
li.remove(22)
print(li)
[11, 33, 22, 44] 只删除第一个元素22
PS: pop 默认从最后一个删除, remove默认左边优先, del li[0] 删除指定索引位置的元素 del li[7:9] 切片整段删除, clear清空列表。
10、 索引取值
li = [11, 22, 33, 22, 44]
print(li[3])
33
11,切片,切片结果也是列表
li = [11, 22, 33, 22, 44]
print(li[2:4]) 取值的索引范围 大于等2,小于4.
[33,22]
二、元组功能及方法
元组,元素不可被修改,不能被增加或者删除
tuple
tu = (11,22,33,44)
tu.count(22),获取指定元素在元组中出现的次数
tu.index(22)
三、字典的功能和方法
# 字典
# dict
# dict
# dic = {
# "k1": 'v1',
# "k2": 'v2'
# }
# 1 根据序列,创建字典,并指定统一的值
# v = dict.fromkeys(["k1",123,"999"],123)
# print(v)
# 2 根据Key获取值,key不存在时,可以指定默认值(None)
# v = dic['k11111']
# print(v)
# v = dic.get('k1',111111)
# print(v)
# 3 删除并获取值
# dic = {
# "k1": 'v1',
# "k2": 'v2'
# }
# v = dic.pop('k1',90)
# print(dic,v)
# k,v = dic.popitem()
# print(dic,k,v)
# 4 设置值,
# 已存在,不设置,获取当前key对应的值
# 不存在,设置,获取当前key对应的值
# dic = {
# "k1": 'v1',
# "k2": 'v2'
# }
# v = dic.setdefault('k1111','123')
# print(dic,v)
# 5 更新
# dic = {
# "k1": 'v1',
# "k2": 'v2'
# }
# dic.update({'k1': '111111','k3': 123})
# print(dic)
# dic.update(k1=123,k3=345,k5="asdf")
# print(dic)
# 6 keys() 7 values() 8 items() get update
##########
# 1、基本机构
# info = {
# "k1": "v1", # 键值对
# "k2": "v2"
# }
#### 2 字典的value可以是任何值
# info = {
# "k1": 18,
# "k2": True,
# "k3": [
# 11,
# [],
# (),
# 22,
# 33,
# {
# 'kk1': 'vv1',
# 'kk2': 'vv2',
# 'kk3': (11,22),
# }
# ],
# "k4": (11,22,33,44)
# }
# print(info)
#### 3 布尔值(1,0)、列表、字典不能作为字典的key
# info ={
# 1: 'asdf',
# "k1": 'asdf',
# True: "123",
# # [11,22]: 123
# (11,22): 123,
# # {'k1':'v1'}: 123
#
# }
# print(info)
# 4 字典无序
# info = {
# "k1": 18,
# "k2": True,
# "k3": [
# 11,
# [],
# (),
# 22,
# 33,
# {
# 'kk1': 'vv1',
# 'kk2': 'vv2',
# 'kk3': (11,22),
# }
# ],
# "k4": (11,22,33,44)
# }
# print(info)
# 5、索引方式找到指定元素
# info = {
# "k1": 18,
# 2: True,
# "k3": [
# 11,
# [],
# (),
# 22,
# 33,
# {
# 'kk1': 'vv1',
# 'kk2': 'vv2',
# 'kk3': (11,22),
# }
# ],
# "k4": (11,22,33,44)
# }
# # v = info['k1']
# # print(v)
# # v = info[2]
# # print(v)
# v = info['k3'][5]['kk3'][0]
# print(v)
# 6 字典支持 del 删除
# info = {
# "k1": 18,
# 2: True,
# "k3": [
# 11,
# [],
# (),
# 22,
# 33,
# {
# 'kk1': 'vv1',
# 'kk2': 'vv2',
# 'kk3': (11,22),
# }
# ],
# "k4": (11,22,33,44)
# }
# del info['k1']
#
# del info['k3'][5]['kk1']
# print(info)
# 7 for循环
# dict
# info = {
# "k1": 18,
# 2: True,
# "k3": [
# 11,
# [],
# (),
# 22,
# 33,
# {
# 'kk1': 'vv1',
# 'kk2': 'vv2',
# 'kk3': (11,22),
# }
# ],
# "k4": (11,22,33,44)
# }
# for item in info:
# print(item)
#
# for item in info.keys():
# print(item)
# for item in info.values():
# print(item)
# for item in info.keys():
# print(item,info[item])
# for k,v in info.items():
# print(k,v)
# True 1 False 0
# info ={
# "k1": 'asdf',
# True: "123",
# # [11,22]: 123
# (11,22): 123,
# # {'k1':' v1'}: 123
#
# }
# print(info)