Python gist

easy_initialize.py

class Structure:
    
    # Class variable that specifies expected fields.
    _fields= []
    def __init__(self, *args):
        if len(args) != len(self._fields):
            raise TypeError('Expected {} arguments'.format(len(self._fields)))
            
        # Set the arguments.
        for name, value in zip(self._fields, args):
            setattr(self, name, value)


# Class definitions
# ----------------------------------------------------------------------------
# class Point(Structure):
#     _fields = ['x', 'y']
# 
# class Circle(Structure):
#     _fields = ['radius']
#     
#     def area(self):
#         return math.pi * self.radius ** 2
# ----------------------------------------------------------------------------

# Usage
# ----------------------------------------------------------------------------
# p = Point(1, 2)
# c = Circle(3)
# ----------------------------------------------------------------------------

easy_initialize_with_kwargs.py

# Solution 1
# Map the keyword arguments corresponding to the attribute names specified in `_fields`.
# --------------------------------------------------------------------------------------

class Structure:
    _fields= []
    
    def __init__(self, *args, **kwargs):
        if len(args) > len(self._fields):
            raise TypeError('Expected {} arguments'.format(len(self._fields)))
            
        # Set all of the positional arguments.
        for name, value in zip(self._fields, args):
            setattr(self, name, value)
            
        # Set the remaining keyword arguments.
        for name in self._fields[len(args):]:
            setattr(self, name, kwargs.pop(name))
            
        # Check for any remaining unknown arguments
        if kwargs:
            raise TypeError('Invalid argument(s): {}'.format(','.join(kwargs)))
			
# Usage 
# ----------------------------------------------------------------------------- 
# class ABC(Structure):
#     _fields = ['A', 'B', 'C']
#
# s1 = ABC('a', 'b', 'c')
# s2 = ABC('a', 'b', C='c')
# s3 = ABC('a', B='b', C='c')
# ----------------------------------------------------------------------------- 


# Solution 2
# Use keyword arguments as additional attributes to the structure not specified in `_fields`.
# -------------------------------------------------------------------------------------------

class Structure:
    _fields= []
    
    def __init__(self, *args, **kwargs):
        if len(args) != len(self._fields):
            raise TypeError('Expected {} arguments'.format(len(self._fields)))

        # Set the arguments.
        for name, value in zip(self._fields, args):
            setattr(self, name, value)

        # Set the additional arguments (if any).
        extra_args = kwargs.keys() - self._fields
        for name in extra_args:
            setattr(self, name, kwargs.pop(name))
        if kwargs:
            raise TypeError('Duplicate values for {}'.format(','.join(kwargs)))

# Usage 
# ----------------------------------------------------------------------------- 			
# class Stock(Structure):
#     _fields = ['name', 'shares', 'price']
#     
# s1 = Stock('ACME', 50, 91.1)
# s2 = Stock('ACME', 50, 91.1, date='8/2/2012')
# -----------------------------------------------------------------------------