Quick enumerations of constant values (pwkit.simpleenum)

The pwkit.simpleenum module contains a single decorator function for creating “enumerations”, by which we mean a group of named, un-modifiable values. For example:

from pwkit.simpleenum import enumeration

@enumeration
class Constants (object):
  period_days = 2.771
  period_hours = period_days * 24
  n_iters = 300
  # etc

def myfunction ():
  print ('the period is', Constants.period_hours, 'hours')

The class declaration syntax is handy here because it lets you define new values in relation to old values. In the above example, you cannot change any of the properties of Constants once it is constructed.

Important

If you populate an enumeration with a mutable data type, however, we’re unable to prevent you from modifying it. For instance, if you do this:

@enumeration
class Dangerous (object):
  mutable = [1, 2]
  immutable = (1, 2)

You can then do something like write Dangerous.mutable.append (3) and modify the value stored in the enumeration. If you’re concerned about this, make sure to populate the enumeration with immutable classes such as tuple, frozenset, int, and so on.

pwkit.simpleenum.enumeration(cls)

A very simple decorator for creating enumerations. Unlike Python 3.4 enumerations, this just gives a way to use a class declaration to create an immutable object containing only the values specified in the class.

If the attribute __pickle_compat__ is set to True in the decorated class, the resulting enumeration value will be callable such that EnumClass(x) = x. This is needed to unpickle enumeration values that were previously implemented using enum.Enum.