Python中的Enum类|极客笔记

Python中的Enum类

什么是Enum

在Python中，枚举是一组命名的值，用于表示有限集合的可能结果。例如，假设我们正在编写一个需要表示一周中的天的程序，我们可以定义一个包含七个命名值的枚举：星期一、星期二、星期三、星期四、星期五、星期六和星期日。

枚举允许您以比仅使用字符串或整数更有意义的方式处理这些值。例如，您可以使用==运算符比较两个星期几，并且它会按预期运行：

Enum的特点

用户可以使用 type() 来检查枚举的类型
通过使用关键字’ name ‘ ，用户可以显示枚举的名称。
枚举是对象的可评估字符串表示，称为 repr() 。

示例：创建枚举的Enum类

import enum
# we will use enum class for creating enumerations
class Weekdays(enum.Enum):
   Sunday = 1
   Monday = 2
   Tuesday = 3
   Wednesday = 4
   Thursday = 5
   Friday = 6
   Saturday = 7
# we will print the enum member as the string
print (" The member of Enum class as the string is : ",end = " ")
print (Weekdays.Monday)

# we will print the enum member as a repr object
print (" The member of Enum class as a repr is : ",end = " ")
print (repr(Weekdays.Sunday))

# now we will check the type of enum member
print (" The type of the member of Enum class is : ",end = " ")
print (type(Weekdays.Saturday))

# we will print name of enum member
print (" The name of the member of Enum class is : ",end = " ")
print (Weekdays.Friday.name)

输出：

The member of Enum class as the string is : Weekdays.Monday
The member of Enum class as a repr is : 
The type of the member of Enum class is : 
The name of the member of Enum class is : Friday

示例2：如何将Enum打印为可迭代列表

用户可以将Enum类作为可迭代列表进行打印。

在下面的示例中，我们将使用for循环来打印Enum类的所有成员。

代码

import enum
# we will user enum class for creating enumerations
class Weekdays(enum.Enum):
   Sunday = 1
   Monday = 2
   Tuesday = 3
   Wednesday = 4
   Thursday = 5
   Friday = 6
   Saturday = 7
# now we will print all enum members by using for loop
print (" The member of Enum class are : ")
for weekday in (Weekdays):
   print(weekday)

输出：

The member of Enum class are : 
Weekdays.Sunday
Weekdays.Monday
Weekdays.Tuesday
Weekdays.Wednesday
Weekdays.Thursday
Weekdays.Friday
Weekdays.Saturday

示例3：如何对枚举类进行哈希

枚举类的成员被称为枚举，也是可哈希的。因此，这些成员可以用于集合和字典。

代码

import enum
# we will use enum class for creating enumerations
class Days(enum.Enum):
   Sunday = 1
   Monday = 2
# we will Hash for creating a dictionary
Daytype = {}
Daytype[Days.Sunday] = 'Sun God'
Daytype[Days.Monday] = 'Mon God'
# now we will Check if the hashing is successful
if Daytype =={Days.Sunday:'Sun God',Days.Monday:'Mon God'}:
 print (" Enum class is hashed ")
else: print (" Enum class is not hashed ")

输出：

Enum class is hashed

示例4：如何访问枚举成员

用户可以通过使用成员项的值或名称来访问Enum类的成员。枚举的名称用作索引。

代码

import enum
# we will use enum class for creating enumerations
class Days(enum.Enum):
  Sunday = 1
  Monday = 2
  Tuesday = 3
  Wednesday = 4
  Thursday = 5 
  Friday = 6
  Saturday = 7
print('The member of Enum class accessed by name: ')
print (Days['Monday'])
print('The member of Enum class accessed by name: ')
print (Days['Friday'])
print('The member of Enum class accessed by Value: ')
print (Days(1))
print('The member of Enum class accessed by Value: ')
print (Days(5))

输出：

The member of Enum class accessed by name: 
Days.Monday
The member of Enum class accessed by name: 
Days.Friday
The member of Enum class accessed by Value: 
Days.Sunday
The member of Enum class accessed by Value: 
Days.Thursday

示例5：如何比较枚举

要比较枚举，我们使用以下方法：

使用” == “和” != “运算符
使用” is “运算符
使用” in “运算符

代码

import enum
# we will use enum class for creating enumerations
class Days(enum.Enum):
  Sunday = 1
  Monday = 2
  Tuesday = 1
  Wednesday = 4
  Thursday = 5 
  Friday = 4
  Saturday = 7
if Days.Sunday == Days.Tuesday:
   print('Match')
else: print ('Do not Match')
if Days.Monday != Days.Tuesday:
    print('Do not Match')
else: print ('Match')
if Days.Wednesday == Days.Friday:
   print('Match')
else: 
print ('Do not Match')
if Days.Thursday != Days.Friday:
    print('Do not Match')
else: 
print ('Match')

输出：