python——60个知识点奠定基础（三）

本文转载：https://xiaochuhe.blog.csdn.net/article/details/122530524
一、知识点21~25

#21.列表list取值嵌套
a = [['1','2'],['3','4']]
print (a)
print (a[0])
print (a[0][0])#第一个列表内取值第一个值
 
#22.练习：八个对象随机分配到三个库，应用random库
import random
offices =[[],[],[]]
names = ["a","b","c","d","e","f","g","d"]
for name in names:
    a = random.randint(0,2)
    offices[a].append(name)#i = 1
for office in offices:
    print("分配个数为%d"%(len(office)),"-"*20)  #i += 1
for name in office:
    print("对象名字：%s"%name)
    #print("\n")
    print("-"*20)
 
#23.元组tuple的增删改查
a = (1,2,3,'青鸟')
b = (4,)
a = a + b #增
print (a)
# del a 删除整个元组
 
#24.元组的转换
a = [1,2]
a = tuple()
print (a,type(a))
 
#25.字典知识点：dict 存储形式（key，value）键值对
dict = {'name':'xiaochuhe','age':'21'}
print (dict['name'])#防止访问对象不存在print(dict.get("age"))
print(dict.get("a","22"))   #未找到设定默认值

输出结果：

二、知识点26~30

#26.字典的修改
dict = {'name':'xiaochuhe','age':'21'}
add = input("新的信息是：")
dict['name'] = add
print (dict['name'],dict)
 
#27.字典的删除
dict = {'name':'xiaochuhe','age':'21'}
print("删除前：{name}：{age}".format(**dict))
del dict['name']#删除一个键值
print (dict)
dict.clear()#清空字典内容
print (dict)
 
#28.字典的增加
dict = {'name':'xiaochuhe','age':'21'}
dict['hobby']='learning'
print (dict)
 
#29.字典的查
dict = {'name':'xiaochuhe','age':'21'}
print (dict.keys())#得到所有的键
print (dict.values())#得到所有的值
print (dict.items())#得到所有的键值对
 
#30.遍历字典所有的键值对
dict = {'name':'xiaochuhe','age':'21'}
for keys in dict.keys():#遍历键
    print (keys,end='')
print ('\n---------------------------')
for keys in dict.values():#遍历值
    print (keys,end='')
print ('\n---------------------------')
for keys in dict.items():#遍历键值对
    print (keys,end='')
print ('\n---------------------------')

输出结果：