Python教程-Python中的枚举类

什么是枚举？

在Python中，枚举是一组具有名称的值，用来表示有限的一组可能结果。例如，假设我们正在编写一个需要表示一周中的日期的程序，我们可以定义一个包含七个命名值的枚举：Monday、Tuesday、Wednesday、Thursday、Friday、Saturday和Sunday。

枚举允许您以比仅使用字符串或整数更有意义的方式使用这些值。例如，您可以使用等于运算符比较两个星期中的日期，并且它将按预期工作：

枚举的特点：

• 用户可以使用 type() 检查枚举的类型。
• 使用 'name' 关键字，用户可以显示枚举的名称。
• 枚举是对象的可求值字符串表示，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类打印为可迭代列表。

在以下示例中，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

Enum类的成员称为Enumeration，并且可哈希。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Enum成员

用户可以通过值或成员项的名称访问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，我们可以使用以下方法：

1. 使用 "==" 和 "!=" 运算符
2. 使用 "is" 运算符
3. 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：

Match
Do not Match
Match
Do not Match

结论

在本文中，我们探讨了Python中的枚举类，它允许我们在代码中定义和操作枚举。通过使用枚举，我们可以使代码更加可读，减少错误，并提供额外的类型安全性。