Python-Design-Patterns catalog
catalog Model
Python-Design-Patterns catalog
# file: 'catalog.py'
#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
A class that uses different static function depending of a parameter passed in
init. Note the use of a single dictionary instead of multiple conditions
"""
class Catalog(object):
"""catalog of multiple static methods that are executed depending on an init
parameter
"""
def __init__(self, param):
# dictionary that will be used to determine which static method is
# to be executed but that will be also used to store possible param
# value
self._static_method_choices = {'param_value_1': self._static_method_1, 'param_value_2': self._static_method_2}
# simple test to validate param value
if param in self._static_method_choices.keys():
self.param = param
else:
raise ValueError("Invalid Value for Param: {0}".format(param))
@staticmethod
def _static_method_1():
print("executed method 1!")
@staticmethod
def _static_method_2():
print("executed method 2!")
def main_method(self):
"""will execute either _static_method_1 or _static_method_2
depending on self.param value
"""
self._static_method_choices[self.param]()
# Alternative implementation for different levels of methods
class CatalogInstance(object):
"""catalog of multiple methods that are executed depending on an init
parameter
"""
def __init__(self, param):
self.x1 = 'x1'
self.x2 = 'x2'
# simple test to validate param value
if param in self._instance_method_choices:
self.param = param
else:
raise ValueError("Invalid Value for Param: {0}".format(param))
def _instance_method_1(self):
print("Value {}".format(self.x1))
def _instance_method_2(self):
print("Value {}".format(self.x2))
_instance_method_choices = {'param_value_1': _instance_method_1, 'param_value_2': _instance_method_2}
def main_method(self):
"""will execute either _instance_method_1 or _instance_method_2
depending on self.param value
"""
self._instance_method_choices[self.param].__get__(self)()
class CatalogClass(object):
"""catalog of multiple class methods that are executed depending on an init
parameter
"""
x1 = 'x1'
x2 = 'x2'
def __init__(self, param):
# simple test to validate param value
if param in self._class_method_choices:
self.param = param
else:
raise ValueError("Invalid Value for Param: {0}".format(param))
@classmethod
def _class_method_1(cls):
print("Value {}".format(cls.x1))
@classmethod
def _class_method_2(cls):
print("Value {}".format(cls.x2))
_class_method_choices = {'param_value_1': _class_method_1, 'param_value_2': _class_method_2}
def main_method(self):
"""will execute either _class_method_1 or _class_method_2
depending on self.param value
"""
self._class_method_choices[self.param].__get__(None, self.__class__)()
class CatalogStatic(object):
"""catalog of multiple static methods that are executed depending on an init
parameter
"""
def __init__(self, param):
# simple test to validate param value
if param in self._static_method_choices:
self.param = param
else:
raise ValueError("Invalid Value for Param: {0}".format(param))
@staticmethod
def _static_method_1():
print("executed method 1!")
@staticmethod
def _static_method_2():
print("executed method 2!")
_static_method_choices = {'param_value_1': _static_method_1, 'param_value_2': _static_method_2}
def main_method(self):
"""will execute either _static_method_1 or _static_method_2
depending on self.param value
"""
self._static_method_choices[self.param].__get__(None, self.__class__)()
def main():
"""
>>> c = Catalog('param_value_1').main_method()
executed method 1!
>>> Catalog('param_value_2').main_method()
executed method 2!
"""
test = Catalog('param_value_2')
test.main_method()
test = CatalogInstance('param_value_1')
test.main_method()
test = CatalogClass('param_value_2')
test.main_method()
test = CatalogStatic('param_value_1')
test.main_method()
if __name__ == "__main__":
main()
### OUTPUT ###
# executed method 2!
# Value x1
# Value x2
# executed method 1!
catalog.py
