Merge branch 'master' of https://github.com/kopok2/PythonCourse

Author: kopok2

Lecture13.md

@@ -14,4 +14,306 @@ KN Pythona wita na kursie Pythona.
 
 Plan:
 
-+ Zarządzane atrybuty
++ Zarządzane atrybuty
+
+
+# Po co zarządza się atrybutami?
+
+```python
+person.name # pobranie wartości
+person.name = wartość # przypisanie wartości
+```
+
+
+# Czym jest obiekt?
+
+```python
+{
+	atrybut
+	metoda
+	{
+		atrybut
+	}
+}
+```
+
+
+
+# Zarządzanie dostępem
+
+```python
+class Person:
+	def get_name(self):
+		if not valid(self.name):
+			raise TypeError()
+		else:
+			return self.name.transform()
+	def set_name(self, value):
+		if not valid(value):
+			raise TypeError()
+		else:
+			self.name = transform(value)
+```
+
+
+
+# Kod wykonywalny w miejscu dostępu
+
+Inne podejścia:
+
+- Metody _getattr_ oraz _setattr_
+- Metoda _getattribute_
+- Funkcja property
+- Protokół deskryptora
+
+
+
+# Właściwości
+
+```python
+attribute = property(fget, fset, fdel, doc)
+```
+
+
+# Właściwości
+
+```python
+class Person:
+	def __init__(self, name):
+		self._name = name
+	def get_name(self):
+		return self._name	
+	def set_name(self, value):
+		self._name = value
+	def del_name(self):
+		del self._name
+	name = property(get_name, set_name, del_name, 'name')
+```
+
+
+# Obliczanie atrybutów
+
+```python
+class PropSquare:
+	def __init__(self, start):
+		self.value = start
+	def get_x(self):
+		return self.value ** 2
+	def set_x(self, value):
+		self.value = value
+	x = property(get_x, set_x)
+```
+
+
+# Właściwości jako dekoratory
+
+```python
+class Person:
+	def __init__(self, name):
+		self._name = name
+	@property
+	def name(self):
+		"Dokumentacja name"
+		return self._name
+	@name.setter
+	def name(self, value):
+		self._name = value
+	@name.deleter
+	def name(self):
+		del self._name
+```
+
+
+# Deskryptory
+
+Właściwości są uproszczonymi deskryptorami.
+
+
+# Deskryptory
+
+```python
+class Descriptor:
+	'Doc string'
+	def __get__(self, instance, owner): ...
+	def __set__(self, instance, value): ...
+	def __delete__(self, instance): ...
+```
+
+
+# Deskryptory
+
+```python
+class Descriptor:
+	def __get__(self, instance, owner):
+		print(self, instance, owner)
+class Subject:
+	attr = Descriptor()
+x = Subject()
+x.attr
+# <..main..Descriptor <main subject <class Subject
+Subject.attr
+# <..main..Descriptor None <class Subject
+```
+
+
+# Deskryptory
+
+```python
+class D:
+	def __get__(*args): print('hop')
+class C:
+	a = D()
+X = C()
+X.a # hop
+C.a # hop
+X.a = 99
+X.a # 99
+C.a # hop
+```
+
+
+# Deskryptory tylko do odczytu
+
+```python
+class D:
+	def __get__(*args): return 1234
+	def __set__(*args): raise AttributeError()
+class C:
+	a = D()
+x = C()
+x.a # 1234
+x.a = 12 # AttributeError...
+```
+
+
+# Deskrtyptory
+
+```python
+class Name:
+	def __get__(self, instance, owner):
+		return instance._name
+	def __set__(self, instance, value):
+		instance._name = value
+	def __delete__(self, instance):
+		del instance._name
+class Person:
+	name = Name()
+```
+
+
+# Deskryptory a klasy osadzone
+
+```python
+class A:
+	class B:
+		def __get__(*args): return 1234
+	a = B()
+```
+
+
+# Informacja o stanie w deskryptorze
+
+```python
+class B:
+	def __init__(self):
+		self.cnt = 0
+	def __get__(*args):
+		self.cnt += 1
+		print(self.cnt)
+		return 1234
+class A:
+	a = B()
+x = A()
+x.a # 1 1234
+x.a # 2 1234
+```
+
+
+# Metody getattr oraz getattribute
+
+Różnica:
+
+- metoda _getattr_: niezdefiniowane atrybuty
+- metoda _getattribute_: każdy atrybut
+
+
+
+# Zarządzanie atrybutami
+
+```python
+def __getattr__(self, name) # niezdefiniowane
+def __getattribute__(self, name) # wszystkie
+def __setattr__(self, name, value) # wszystkie
+def __delattr__(self, name) # wszystkie
+```
+
+
+# Zarządzane atrybuty
+
+```python
+class Wrapper:
+	def __init__(self, object):
+		self.wrapped = object
+	def __getattr__(self, attrname):
+		print('Śledzenie: ' + attrname)
+		return getattr(self.wrapped, attrname)
+```
+
+
+
+# Zagadka
+
+```python
+class A:
+	def __getattribute__(self, name):
+		return self.other
+x = A()
+print(x.abc)
+```
+
+
+# Zagadka - rozwiązanie
+
+```python
+RecursionError !
+```
+
+
+
+# Zagadka - kod
+
+```python
+class A:
+	def __getattribute__(self, name):
+		return object.__getattribute__(self, 'other')
+```
+
+
+
+# Pętla nr 2
+
+```python
+class A:
+	def __setattr__(self, attrname, value):
+		self.other = value # pętla!
+```
+
+
+# Pętla nr 2 - rozwiązanie
+
+```python
+class A:
+	def __setattr__(self, attrname, value):
+		self.__dict__['other'] = value
+```
+
+
+# Pętla nr 1 - CD
+
+```python
+class A:
+	def __getattribute__(self, attrname):
+		return self.__dict__[attrname] # ?
+```
+
+