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I have an enum 

class Nationality: Poland='PL' Germany='DE' France='FR' ... Spain='ES'

I have 2 prototypes of methods: 

# I want somethink like in c# def convert_country_code_to_country_name(country_code): print Enum.Parse(typeof(Nationality),country_code) #this a second solution ,but it has a lot of ifs def convert_country_code_to_country_name(country_code): if country_code=='DE': print Nationality.Germany #btw how to print here 'Germany', instead 'DE'

This is how I want call this method:

convert_country_code_to_country_name('DE') # I want here to print 'Germany'

How to implement it in python?

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    What have you tried? Please post the Python code you tried. We don't like to write code for you. However, we'll help you solve problems with code you've written. Commented Feb 24, 2011 at 12:45
  • 1
    S.Lott and many other people do not like writing code for you. Some people actually enjoy writing code for other, free of charge. However, the solution you get might not be what you want ... Commented Feb 24, 2011 at 12:47

6 Answers 6

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6

The best solution would be to create a dictionary right from the start. Your enum doesn't make sense in Python, its just unnecessarily complex. It looks like you are trying to write Java code, which is quite the opposite of what Python code is supposed to look like.

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4 Comments

But what if I want this nationality enum in many modules. Isi is a good idea to write it in every module? I'm c# programmer, so I know that I don't get python conception in full
@user: You can create the dictionary only once and then import it in other modules - it doesn't make a difference if it is a class or not. In general working in a dynamic language like Python can be very different from Java or C#. It takes some time to get used to it, but in the end it is well worth the effort and makes you an overall better programmer.
You have right, but when I stop using enum, then I lost autocomplete from ide and I don't wanna that.
@user: Unfortunately autocomplete will never work as well in a dynamic language compared to a static language. So I wouldn't try too hard not to break it, since otherwise you might again end up with Java code. It's simply one of the downsides of dynamic languages.
4

Python 3.4 has a new Enum data type (which has been backported), which easily supports your use case:

class Nationality(enum.Enum): Poland = 'PL' Germany = 'DE' France = 'FR' Spain = 'ES'

To get the enum member from the name:

--> Nationality['France'] <Nationality.France: 'FR'>

To get the enum member from the value:

--> Nationalatiy('FR') <Nationality.France: 'FR'>

And once you have the enum member:

--> member = Nationality('FR') --> member.name 'France' --> member.value 'FR'
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class Nationality: Poland='PL' Germany='DE' France='FR' Spain='ES' nationalityDict = {} for k, v in Nationality.__dict__.iteritems(): if not k.startswith('__'): nationalityDict[v] = k

And now: nationalityDict['DE'] contains Germany.

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nationalityDict = {v: k for k, v in vars(Nationality).items() if k[:2] != '__'}
nationalityDict = dict((v, k) for k, v in vars(Nationality).items() if k[:2] != '__') - for Python 2.6 and older...
2

Would you like to use dict instead?

Nationality = { "PL" : "Poland", "DE": "Germany"} print Nationality["DE"] # prints 'Germany'
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No, because I use this enum in others module, and I don't want to duplicate code
1

My approach would be like this one (maybe not perfect, but you get the idea):

class Nationality: Poland = 'PL' Germany = 'DE' France = 'FR' def convertToCodeFromName(name): return getattr(Nationality, name) def convertToNameFromCode(code): lookFor = None for member in dir(Nationality): if (getattr(Nationality, member) == code): lookFor = member break return lookFor print(Nationality.convertToCodeFromName("Poland")) print(Nationality.convertToNameFromCode("PL"))

Hope this helps.

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0

How about a pure method for converting to enum? Just stash this in a util lib. Or you could put it on a base Enum class and have target_enum default to self.

Could also tweak this to raise an exception instead of using the default value, but the default worked better for my specific case.

from enum import Enum def to_enum(v,target_enum,default = None): ''' if v is given enum, return it if v is an int, convert to enum via int convert if v is str convert to enum via string convert ''' ret = default if v is None: return ret if v in target_enum: return v try: return target_enum(int(v)) except Exception: pass try: return target_enum[str(v)] except Exception: pass return ret

Here is the unittest class for it.

import unittest from enum import Enum,unique class EnumTest(Enum): T0 = 0 T1 = 1 class EnumTest2(Enum): T0 = 0 T1 = 1 class EnumUtilTest(unittest.TestCase): def test_to_enum(self): '''str, int, and Enum should be convertable ''' r = Util.to_enum(1,EnumTest) self.assertEqual(r,EnumTest.T1) r = Util.to_enum('T1',EnumTest) self.assertEqual(r,EnumTest.T1) r = Util.to_enum(EnumTest.T1,EnumTest) self.assertEqual(r,EnumTest.T1) r = Util.to_enum('1',EnumTest) self.assertEqual(r,EnumTest.T1) def test_to_enum_fail(self): '''Return None if convert fails''' self.assertIsNone(Util.to_enum( None,EnumTest )) self.assertIsNone(Util.to_enum( 'abd',EnumTest )) self.assertIsNone(Util.to_enum( 123,EnumTest )) self.assertIsNone(Util.to_enum( EnumTest2.T1,EnumTest )) def test_to_enum_default(self): '''test default param''' r = Util.to_enum(EnumTest2.T1,EnumTest,EnumTest.T0) self.assertEqual(r,EnumTest.T0) if __name__ == '__main__': unittest.main()
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