Enumerant names shall be uppercase

[rgeronimi]

This python doc indicates that enumerant names are lowercase:

iso4217/iso4217/__init__.py

Line 108 in 7a546bb

some special currencies like ```XXX``. Enumerants names are lowercase

This creates 2 issues:

• A syntactic one - in Python syntactic conventions are that enum members shall be uppercase
• A computational one - if one wants to check if a currency code exists in the enum without triggering a not-found exception, the proper way is to use Currency.__members__.get(code) and check its return value for None. However the current convention requires first to convert the code to lowercase just to be able to lookup the code

Changing the convention to uppercase automatically eliminates these 2 issues, plus simplifies the code (call to lower() useless now).

[dahlia]

That's a good point, but it wouldn't be that easy to change the casing due to backwards compatibility. I'm going to add a new function to address the second issue.

[olliemath]

if one wants to check if a currency code exists in the enum without triggering a not-found exception, the proper way is to use Currency.__members__.get(code) and check its return value for None.

Just passing by, but note this isn't the proper way to check if an enum value (rather than key) is present, instead use

code in Currency._value2member_map_

for example

>>> from iso4217 import Currency
>>> "USD" in Currency._value2member_map_
True
>>> "XYZ" in Currency._value2member_map_
False

or just wrap Currency(code) in a try/except clause.