How to convert int to Enum in python?
Question:
Using the new Enum feature (via backport enum34) with python 2.7.6.
Given the following definition, how can I convert an int to the corresponding Enum value?
from enum import Enum
class Fruit(Enum):
Apple = 4
Orange = 5
Pear = 6
I know I can hand craft a series of if-statements to do the conversion but is there an easy pythonic way to convert? Basically, I’d like a function ConvertIntToFruit(int) that returns an enum value.
My use case is I have a csv file of records where I’m reading each record into an object. One of the file fields is an integer field that represents an enumeration. As I’m populating the object I’d like to convert that integer field from the file into the corresponding Enum value in the object.
Answers:
You ‘call’ the Enum
class:
Fruit(5)
to turn 5
into Fruit.Orange
:
>>> from enum import Enum
>>> class Fruit(Enum):
... Apple = 4
... Orange = 5
... Pear = 6
...
>>> Fruit(5)
<Fruit.Orange: 5>
From the Programmatic access to enumeration members and their attributes section of the documentation:
Sometimes it’s useful to access members in enumerations
programmatically (i.e. situations where Color.red
won’t do because the
exact color is not known at program-writing time). Enum
allows such
access:
>>> Color(1)
<Color.red: 1>
>>> Color(3)
<Color.blue: 3>
In a related note: to map a string value containing the name of an enum member, use subscription:
>>> s = 'Apple'
>>> Fruit[s]
<Fruit.Apple: 4>
I think it is in simple words is to convert the int
value into Enum
by calling EnumType(int_value)
, after that access the name
of the Enum
object:
my_fruit_from_int = Fruit(5) #convert to int
fruit_name = my_fruit_from_int.name #get the name
print(fruit_name) #Orange will be printed here
Or as a function:
def convert_int_to_fruit(int_value):
try:
my_fruit_from_int = Fruit(int_value)
return my_fruit_from_int.name
except:
return None
I wanted something similar so that I could access either part of the value pair from a single reference. The vanilla version:
#!/usr/bin/env python3
from enum import IntEnum
class EnumDemo(IntEnum):
ENUM_ZERO = 0
ENUM_ONE = 1
ENUM_TWO = 2
ENUM_THREE = 3
ENUM_INVALID = 4
#endclass.
print('Passes')
print('1) %d'%(EnumDemo['ENUM_TWO']))
print('2) %s'%(EnumDemo['ENUM_TWO']))
print('3) %s'%(EnumDemo.ENUM_TWO.name))
print('4) %d'%(EnumDemo.ENUM_TWO))
print()
print('Fails')
print('1) %d'%(EnumDemo.ENUM_TWOa))
The failure throws an exception as would be expected.
A more robust version:
#!/usr/bin/env python3
class EnumDemo():
enumeration = (
'ENUM_ZERO', # 0.
'ENUM_ONE', # 1.
'ENUM_TWO', # 2.
'ENUM_THREE', # 3.
'ENUM_INVALID' # 4.
)
def name(self, val):
try:
name = self.enumeration[val]
except IndexError:
# Always return last tuple.
name = self.enumeration[len(self.enumeration) - 1]
return name
def number(self, val):
try:
index = self.enumeration.index(val)
except (TypeError, ValueError):
# Always return last tuple.
index = (len(self.enumeration) - 1)
return index
#endclass.
print('Passes')
print('1) %d'%(EnumDemo().number('ENUM_TWO')))
print('2) %s'%(EnumDemo().number('ENUM_TWO')))
print('3) %s'%(EnumDemo().name(1)))
print('4) %s'%(EnumDemo().enumeration[1]))
print()
print('Fails')
print('1) %d'%(EnumDemo().number('ENUM_THREEa')))
print('2) %s'%(EnumDemo().number('ENUM_THREEa')))
print('3) %s'%(EnumDemo().name(11)))
print('4) %s'%(EnumDemo().enumeration[-1]))
When not used correctly this avoids creating an exception and, instead, passes back a fault indication. A more Pythonic way to do this would be to pass back “None” but my particular application uses the text directly.
class Status(IntEnum):
UPLOADED = 1
DOWNLOADED = 5
SEGMENTED = 10
DIRECTED = 15
READYTODEEP = 20
to get the enum;
statusId = 5
Status(statusId)
to get the enum’s string value;
statusId = 5
print(Status(statusId).name)
Using the new Enum feature (via backport enum34) with python 2.7.6.
Given the following definition, how can I convert an int to the corresponding Enum value?
from enum import Enum
class Fruit(Enum):
Apple = 4
Orange = 5
Pear = 6
I know I can hand craft a series of if-statements to do the conversion but is there an easy pythonic way to convert? Basically, I’d like a function ConvertIntToFruit(int) that returns an enum value.
My use case is I have a csv file of records where I’m reading each record into an object. One of the file fields is an integer field that represents an enumeration. As I’m populating the object I’d like to convert that integer field from the file into the corresponding Enum value in the object.
You ‘call’ the Enum
class:
Fruit(5)
to turn 5
into Fruit.Orange
:
>>> from enum import Enum
>>> class Fruit(Enum):
... Apple = 4
... Orange = 5
... Pear = 6
...
>>> Fruit(5)
<Fruit.Orange: 5>
From the Programmatic access to enumeration members and their attributes section of the documentation:
Sometimes it’s useful to access members in enumerations
programmatically (i.e. situations whereColor.red
won’t do because the
exact color is not known at program-writing time).Enum
allows such
access:>>> Color(1) <Color.red: 1> >>> Color(3) <Color.blue: 3>
In a related note: to map a string value containing the name of an enum member, use subscription:
>>> s = 'Apple'
>>> Fruit[s]
<Fruit.Apple: 4>
I think it is in simple words is to convert the int
value into Enum
by calling EnumType(int_value)
, after that access the name
of the Enum
object:
my_fruit_from_int = Fruit(5) #convert to int
fruit_name = my_fruit_from_int.name #get the name
print(fruit_name) #Orange will be printed here
Or as a function:
def convert_int_to_fruit(int_value):
try:
my_fruit_from_int = Fruit(int_value)
return my_fruit_from_int.name
except:
return None
I wanted something similar so that I could access either part of the value pair from a single reference. The vanilla version:
#!/usr/bin/env python3
from enum import IntEnum
class EnumDemo(IntEnum):
ENUM_ZERO = 0
ENUM_ONE = 1
ENUM_TWO = 2
ENUM_THREE = 3
ENUM_INVALID = 4
#endclass.
print('Passes')
print('1) %d'%(EnumDemo['ENUM_TWO']))
print('2) %s'%(EnumDemo['ENUM_TWO']))
print('3) %s'%(EnumDemo.ENUM_TWO.name))
print('4) %d'%(EnumDemo.ENUM_TWO))
print()
print('Fails')
print('1) %d'%(EnumDemo.ENUM_TWOa))
The failure throws an exception as would be expected.
A more robust version:
#!/usr/bin/env python3
class EnumDemo():
enumeration = (
'ENUM_ZERO', # 0.
'ENUM_ONE', # 1.
'ENUM_TWO', # 2.
'ENUM_THREE', # 3.
'ENUM_INVALID' # 4.
)
def name(self, val):
try:
name = self.enumeration[val]
except IndexError:
# Always return last tuple.
name = self.enumeration[len(self.enumeration) - 1]
return name
def number(self, val):
try:
index = self.enumeration.index(val)
except (TypeError, ValueError):
# Always return last tuple.
index = (len(self.enumeration) - 1)
return index
#endclass.
print('Passes')
print('1) %d'%(EnumDemo().number('ENUM_TWO')))
print('2) %s'%(EnumDemo().number('ENUM_TWO')))
print('3) %s'%(EnumDemo().name(1)))
print('4) %s'%(EnumDemo().enumeration[1]))
print()
print('Fails')
print('1) %d'%(EnumDemo().number('ENUM_THREEa')))
print('2) %s'%(EnumDemo().number('ENUM_THREEa')))
print('3) %s'%(EnumDemo().name(11)))
print('4) %s'%(EnumDemo().enumeration[-1]))
When not used correctly this avoids creating an exception and, instead, passes back a fault indication. A more Pythonic way to do this would be to pass back “None” but my particular application uses the text directly.
class Status(IntEnum):
UPLOADED = 1
DOWNLOADED = 5
SEGMENTED = 10
DIRECTED = 15
READYTODEEP = 20
to get the enum;
statusId = 5
Status(statusId)
to get the enum’s string value;
statusId = 5
print(Status(statusId).name)