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.
asked May 30, 2014 at 9:50
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]
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[3]
In a related note: to map a string value containing the name of an enum member, use subscription:
>>> s = 'Apple'
>>> Fruit[s]
answered May 30, 2014 at 10:00
Martijn Pieters♦Martijn Pieters
983k273 gold badges3871 silver badges3232 bronze badges
5
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
answered Mar 31, 2019 at 7:55
Ali Ezzat OdehAli Ezzat Odeh
2,0631 gold badge16 silver badges17 bronze badges
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.
answered Sep 13, 2019 at 14:11
1