[Python知识库]Python-字典（1）

1 创建字典

字典是一系列的键值对，每个键都与一个值对应，值可以是数、字符串、列表、字典等

#创建字典,如需要创建一个空的字典students_info={}
students_info={'jack':5,'andy':7,'kiki':6,'alicy':8}
#访问学生年龄
print(students_info.keys())
print(students_info.values())
print(f"Andy is {students_info['andy']} years old.")

运行结果：

dict_keys(['jack', 'andy', 'kiki', 'alicy'])
dict_values([5, 7, 6, 8])
Andy is 7 years old.
?

2 字典操作

#字典操作
students_info={'jack':5,'andy':7,'kiki':6,'alicy':8}
students_info['allen']=7#添加键值对
print(students_info)
students_info['allen']=18#修改allen关联值改为18
print(students_info)
del students_info['allen']#删除allen键值对
print(students_info)

运行结果：
{'jack': 5, 'andy': 7, 'kiki': 6, 'alicy': 8, 'allen': 7}
{'jack': 5, 'andy': 7, 'kiki': 6, 'alicy': 8, 'allen': 18}
{'jack': 5, 'andy': 7, 'kiki': 6, 'alicy': 8}

3 字典访问

（1）get访问

#字典访问
students_info={'jack':5,'andy':7,'kiki':6,'alicy':8}
#访问字典，若没有此键值，返回No this student,若没有指定第二个参数，返回None
student_age=students_info.get('andy', 'No this student.')
print(f"Andy is {student_age} years old.")

运行结果：
Andy is 7 years old.

（2）遍历访问

#创建字典
students_info={'jack':5,'andy':7,'kiki':6,'alicy':8}

#访问字典，若没有此键值，返回No this student,若没有指定第二个参数，返回None
student_age=students_info.get('andy', 'No this student.')
print(f"Andy is {student_age} years old.")

#遍历键值对
students_info={'jack':5,'andy':7,'kiki':7,'alicy':8}

#遍历所有键和值
for key,value in students_info.items():
    print(f"{key} is {value} years old.")

#遍历所有键,临时排序后遍历
for name in sorted(students_info.keys()):
    print(f"student name is {name}")

#遍历所有值
for age in students_info.values():
    print(age)

#查询年龄
students_name=['jack','kiki']
for name in students_name:
    age=students_info[name]
    print(f"{name} is {age} years old.")

#列出不重复的年龄大小，set
for age in set(students_info.values()):
    print(f"不重复的年龄是：{age}")

#判断allen是否有年龄信息记录在案
if 'allen' not in students_info.keys():
    print("Allen`s age is not in the table. \nPlease give information.")

运行结果：

Andy is 7 years old.
jack is 5 years old.
andy is 7 years old.
kiki is 7 years old.
alicy is 8 years old.
student name is alicy
student name is andy
student name is jack
student name is kiki
5
7
7
8
jack is 5 years old.
kiki is 7 years old.
不重复的年龄是：8
不重复的年龄是：5
不重复的年龄是：7
Allen`s age is not in the table.
Please give information.