Python3-2020-测试开发-8- 字典dict

"""

字典：通过键对象，获取对应的值

特点：“键”是任意不可变数据，比如：整数，浮点数，字符串，元组
但是：列表、字典，集合这些可变对象，不能作为键使用，并且“键”不能重复
"""

# 第一种方式
a1 = {‘name‘:‘chu‘,‘age‘:18,‘job‘:‘teacher‘}
print(a1)    # {‘name‘: ‘chu‘, ‘age‘: 18, ‘job‘: ‘teacher‘}

# 第二种方式
a2 = dict(name= ‘chu‘,age=18)
print(a2)    # {‘name‘: ‘chu‘, ‘age‘: 18}

# 第三种方式
a3 = [(‘name‘,‘chu‘),(‘age‘,18)]
print(dict(a3))   # {‘name‘: ‘chu‘, ‘age‘: 18}

# 第四种方式zip()
k = [‘name‘,‘age‘,‘job‘]
v = [‘chu‘,18,‘teacher‘]
a4 = dict(zip(k,v))
print(a4)   # {‘name‘: ‘chu‘, ‘age‘: 18, ‘job‘: ‘teacher‘}

# 通过fromkeys()创建值为空的字典
a5 = dict.fromkeys([‘name‘,‘age‘,‘job‘])
print(a5)     # {‘name‘: None, ‘age‘: None, ‘job‘: None}

b1 = {‘name‘:‘chu‘,‘age‘:18,‘job‘:‘teacher‘}

# 3.1 一般访问，键不存在时，报错
print(b1[‘name‘])    # chu
# print(b1[‘aaaaa‘])   # KeyError: ‘aaaaa‘

# 3.2 通过get()访问，键不存在时，默认返回None，也可自定义返回值
print(b1.get(‘name‘))    # chu
print(b1.get(‘aaaa‘))    # None
print(b1.get(‘aaaa‘,"此键不存在！"))   # 此键不存在！

# 3.3 列出所有的键值对 items()
print(b1.items())     # dict_items([(‘name‘, ‘chu‘), (‘age‘, 18), (‘job‘, ‘teacher‘)])

# 3.4 列出所有的键keys(),值values()
print(b1.keys())     # dict_keys([‘name‘, ‘age‘, ‘job‘])
print(b1.values())   # dict_values([‘chu‘, 18, ‘teacher‘])

# 3.5 len() 字典中有多少个键值对

print(len(b1))  # 3

# 3.6 检测一个“键”是否存在于字典中

print("name" in b1)   # True

# 4.1 添加，如果添加的键存在，则会覆盖旧的键,如果不存在，新增键值对
print("------------------------添加，修改，删除------------------------------")
b2 = {‘name‘:‘chu‘,‘age‘:18,‘job‘:‘teacher‘}
b2["address"] = "三元桥一号院"
print(b2)      # {‘name‘: ‘chu‘, ‘age‘: 18, ‘job‘: ‘teacher‘, ‘address‘: ‘三元桥一号院‘}
b2["name"] = "baobao"
print(b2)    # {‘name‘: ‘baobao‘, ‘age‘: 18, ‘job‘: ‘teacher‘, ‘address‘: ‘三元桥一号院‘}

# 4.2 update() 将新字典中的的所有键值对全部添加到旧的字典中，如果key重复，则直接覆盖
x1 = {‘name‘:‘chu‘,‘age‘:18,‘job‘:‘teacher‘}
x2 = {‘name1‘:‘chu‘,‘age1‘:18,‘job‘:‘teacher01‘}
x1.update(x2)
print(x1)       # {‘name‘: ‘chu‘, ‘age‘: 18, ‘job‘: ‘teacher01‘, ‘name1‘: ‘chu‘, ‘age1‘: 18}
print(x2)       # {‘name1‘: ‘chu‘, ‘age1‘: 18, ‘job‘: ‘teacher01‘}

# 4.3 del():删除字典中的值   pop()： 删除字典中的值并将值返回   clear()：清空字典   popitem():随机删除和返回该键键值对

b3 = {‘name‘: ‘chu‘, ‘age‘: 18, ‘job‘: ‘teacher‘, ‘address‘: ‘三元桥一号院‘}
del(b3[‘name‘])
print(b3)       # {‘age‘: 18, ‘job‘: ‘teacher‘, ‘address‘: ‘三元桥一号院‘}

bb = b3.pop(‘age‘)
print(b3)   #  {‘job‘: ‘teacher‘, ‘address‘: ‘三元桥一号院‘}
print(bb)   # 18
b4 = {‘name‘: ‘chu‘, ‘age‘: 18, ‘job‘: ‘teacher‘, ‘address‘: ‘三元桥一号院‘}

print(b4.popitem())    # (‘address‘, ‘三元桥一号院‘)
print(b4.popitem())    # (‘job‘, ‘teacher‘)
print(b4.popitem())    # (‘age‘, 18)
print(b4.popitem())    # (‘name‘, ‘chu‘)
# print(b4.popitem())    # KeyError: ‘popitem(): dictionary is empty‘

# 5.1 序列解包
a,b,c = 10,20,30
a1,b1,c1 = (20,30,40)
(a2,b2,c2) = (40,50,60)
[a3,b3,c3] = [1,2,3]
print(a,b,c)    # 10 20 30
print(a1,b1,c1) # 20 30 40
print(a2,b2,c2) # 40 50 60
print(a3,b3,c3) # 1 2 3

# 5.2 字典的序列解包时，默认是对键进行操作
# 如果对值进行操作，x.values()
# 如果对键值对进行操作，x.items()

b5 = {‘name‘: ‘chu‘, ‘age‘: 18, ‘job‘: ‘teacher‘, ‘address‘: ‘三元桥一号院‘}

x,y,z,o = b5
print(x,y,z,o)    # name age job address

x1,y1,z1,o1 = b5.values()
print(x1,y1,z1,o1) # chu 18 teacher 三元桥一号院

x2,y2,z2,o2 = b5.items()
print(x2,y2,z2,o2) # (‘name‘, ‘chu‘) (‘age‘, 18) (‘job‘, ‘teacher‘) (‘address‘, ‘三元桥一号院‘)