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# _main.py
import sys
def classinitializer(proc):
# basic idea stolen from zope.interface.advice, which credits P.J. Eby
def newproc(*args, **kw):
frame = sys._getframe(1)
if '__module__' in frame.f_locals and not \
'__module__' in frame.f_code.co_varnames: # we are in a class
if '__metaclass__' in frame.f_locals:
raise SyntaxError("Don't use two class initializers or\n"
"a class initializer together with a__metaclass__ hook")
def makecls(name, bases, dic):
try:
cls = type(name, bases, dic)
except TypeError, e:
if "can't have only classic bases" in str(e):
cls = type(name, bases + (object,), dic)
else: # other strange errors, such as __slots__ conflicts, etc
raise
proc(cls, *args, **kw)
return cls
frame.f_locals["__metaclass__"] = makecls
else:
proc(*args, **kw)
newproc.__name__ = proc.__name__
newproc.__module__ = proc.__module__
newproc.__doc__ = proc.__doc__
newproc.__dict__ = proc.__dict__
return newproc
import datetime
@classinitializer
def def_properties(cls, schema):
"""
Add properties to cls, according to the schema, which is a list
of pairs (fieldname, typecast). A typecast is a
callable converting the field value into a Python type.
The initializer saves the attribute names in a list cls.fields
and the typecasts in a list cls.types. Instances of cls are expected
to have private attributes with names determined by the field names.
"""
cls.fields = []
cls.types = []
for name, typecast in schema:
if hasattr(cls, name): # avoid accidental overriding
raise AttributeError('You are overriding %s!' % name)
def getter(self, name=name):
return getattr(self, '_' + name)
def setter(self, value, name=name, typecast=typecast):
setattr(self, '_' + name, typecast(value))
setattr(cls, name, property(getter, setter))
cls.fields.append(name)
cls.types.append(typecast)
def date(isodate): # add error checking if you like
"Convert an ISO date into a datetime.date object"
return datetime.date(*map(int, isodate.split('-')))
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