chapter 18

KrisNguyen135 · KrisNguyen135 · commit c3559e2300e7 · 2021-11-08T20:54:52.000-06:00
diff --git a/Chapter18/prototype.py b/Chapter18/prototype.py
@@ -0,0 +1,75 @@
+import copy
+
+class Website: 
+    def __init__(self, name, domain, description, author, **kwargs): 
+        '''Examples of optional attributes (kwargs): 
+           category, creation_date, technologies, keywords.
+        ''' 
+        self.name = name 
+        self.domain = domain 
+        self.description = description
+        self.author = author
+        
+        for key in kwargs:
+            setattr(self, key, kwargs[key])
+ 
+    def __str__(self): 
+        summary = [f'Website "{self.name}"\n',] 
+        
+        infos = vars(self).items()
+        ordered_infos = sorted(infos)
+        for attr, val in ordered_infos:
+            if attr == 'name':
+                continue
+            summary.append(f'{attr}: {val}\n')
+            
+        return ''.join(summary) 
+
+        
+class Prototype: 
+    def __init__(self): 
+        self.objects = dict() 
+ 
+    def register(self, identifier, obj): 
+        self.objects[identifier] = obj 
+ 
+    def unregister(self, identifier): 
+        del self.objects[identifier] 
+ 
+    def clone(self, identifier, **attrs): 
+        found = self.objects.get(identifier) 
+        if not found: 
+            raise ValueError(f'Incorrect object identifier: {identifier}') 
+        obj = copy.deepcopy(found) 
+        for key in attrs:
+            setattr(obj, key, attrs[key])
+
+        return obj
+        
+def main(): 
+    keywords = ('python', 'data', 'apis', 'automation')
+    site1 = Website('ContentGardening', 
+            domain='contentgardening.com', 
+            description='Automation and data-driven apps', 
+            author='Kamon Ayeva',
+            category='Blog',
+            keywords=keywords)
+ 
+    prototype = Prototype() 
+    identifier = 'ka-cg-1' 
+    prototype.register(identifier, site1)
+    
+    site2 = prototype.clone(identifier, 
+            name='ContentGardeningPlayground',
+            domain='play.contentgardening.com', 
+            description='Experimentation for techniques featured on the blog', 
+            category='Membership site',
+            creation_date='2018-08-01') 
+ 
+    for site in (site1, site2): 
+        print(site)
+    print(f'ID site1 : {id(site1)} != ID site2 : {id(site2)}')
+    
+if __name__ == '__main__': 
+    main()
+    
diff --git a/Chapter18/singleton.py b/Chapter18/singleton.py
@@ -0,0 +1,56 @@
+
+
+import urllib.parse
+import urllib.request
+
+
+class SingletonType(type):
+    _instances = {}
+    def __call__(cls, *args, **kwargs):
+        if cls not in cls._instances:
+            cls._instances[cls] = super(SingletonType, cls).__call__(*args, **kwargs)
+        return cls._instances[cls]
+
+
+class URLFetcher(metaclass=SingletonType):
+
+    def __init__(self):
+        self.urls = []
+
+    def fetch(self, url):
+        req = urllib.request.Request(url)
+        with urllib.request.urlopen(req) as response:
+            if response.code == 200:
+                the_page = response.read()
+                print(the_page)
+
+                urls = self.urls
+                urls.append(url)
+                self.urls = urls
+
+    def dump_url_registry(self):
+        return ', '.join(self.urls)
+
+
+def main():
+
+    MY_URLS = ['http://google.com', 
+               'http://python.org',
+               'https://www.python.org/error',
+               ]
+
+    print(URLFetcher() is URLFetcher())
+
+    fetcher = URLFetcher()
+    for url in MY_URLS:
+        try:
+            fetcher.fetch(url)
+        except Exception as e:
+            print(e)
+
+    print('-------')
+    done_urls = fetcher.dump_url_registry()
+    print(f'Done URLs: {done_urls}')
+
+if __name__ == '__main__':
+    main()
