@@ -14,4 +14,306 @@ KN Pythona wita na kursie Pythona.
1414
1515Plan:
1616
17- + Zarządzane atrybuty
17+ + Zarządzane atrybuty
18+ 19+ 20+ # Po co zarządza się atrybutami?
21+ 22+ ``` python
23+ person.name # pobranie wartości
24+ person.name = wartość # przypisanie wartości
25+ ```
26+ 27+ 28+ # Czym jest obiekt?
29+ 30+ ``` python
31+ {
32+ atrybut
33+ metoda
34+ {
35+ atrybut
36+ }
37+ }
38+ ```
39+ 40+ 41+ 42+ # Zarządzanie dostępem
43+ 44+ ``` python
45+ class Person :
46+ def get_name (self
47+ if not valid(self .name):
48+ raise TypeError ()
49+ else :
50+ return self .name.transform()
51+ def set_name (self value ):
52+ if not valid(value):
53+ raise TypeError ()
54+ else :
55+ self .name = transform(value)
56+ ```
57+ 58+ 59+ 60+ # Kod wykonywalny w miejscu dostępu
61+ 62+ Inne podejścia:
63+ 64+ - Metody _ getattr_ oraz _ setattr_
65+ - Metoda _ getattribute_
66+ - Funkcja property
67+ - Protokół deskryptora
68+ 69+ 70+ 71+ # Właściwości
72+ 73+ ``` python
74+ attribute = property (fget, fset, fdel, doc)
75+ ```
76+ 77+ 78+ # Właściwości
79+ 80+ ``` python
81+ class Person :
82+ def __init__ (self name ):
83+ self ._name = name
84+ def get_name (self
85+ return self ._name
86+ def set_name (self value ):
87+ self ._name = value
88+ def del_name (self
89+ del self ._name
90+ name = property (get_name, set_name, del_name, ' name'
91+ ```
92+ 93+ 94+ # Obliczanie atrybutów
95+ 96+ ``` python
97+ class PropSquare :
98+ def __init__ (self start ):
99+ self .value = start
100+ def get_x (self
101+ return self .value ** 2
102+ def set_x (self value ):
103+ self .value = value
104+ x = property (get_x, set_x)
105+ ```
106+ 107+ 108+ # Właściwości jako dekoratory
109+ 110+ ``` python
111+ class Person :
112+ def __init__ (self name ):
113+ self ._name = name
114+ @ property
115+ def name (self
116+ " Dokumentacja name"
117+ return self ._name
118+ @name.setter
119+ def name (self value ):
120+ self ._name = value
121+ @name.deleter
122+ def name (self
123+ del self ._name
124+ ```
125+ 126+ 127+ # Deskryptory
128+ 129+ Właściwości są uproszczonymi deskryptorami.
130+ 131+ 132+ # Deskryptory
133+ 134+ ``` python
135+ class Descriptor :
136+ ' Doc string'
137+ def __get__ (self instance , owner ): ...
138+ def __set__ (self instance , value ): ...
139+ def __delete__ (self instance ): ...
140+ ```
141+ 142+ 143+ # Deskryptory
144+ 145+ ``` python
146+ class Descriptor :
147+ def __get__ (self instance , owner ):
148+ print (self , instance, owner)
149+ class Subject :
150+ attr = Descriptor()
151+ x = Subject()
152+ x.attr
153+ # <..main..Descriptor <main subject <class Subject
154+ Subject.attr
155+ # <..main..Descriptor None <class Subject
156+ ```
157+ 158+ 159+ # Deskryptory
160+ 161+ ``` python
162+ class D :
163+ def __get__ (* args ): print (' hop'
164+ class C :
165+ a = D()
166+ X = C()
167+ X.a # hop
168+ C.a # hop
169+ X.a = 99
170+ X.a # 99
171+ C.a # hop
172+ ```
173+ 174+ 175+ # Deskryptory tylko do odczytu
176+ 177+ ``` python
178+ class D :
179+ def __get__ (* args ): return 1234
180+ def __set__ (* args ): raise AttributeError ()
181+ class C :
182+ a = D()
183+ x = C()
184+ x.a # 1234
185+ x.a = 12 # AttributeError...
186+ ```
187+ 188+ 189+ # Deskrtyptory
190+ 191+ ``` python
192+ class Name :
193+ def __get__ (self instance , owner ):
194+ return instance._name
195+ def __set__ (self instance , value ):
196+ instance._name = value
197+ def __delete__ (self instance ):
198+ del instance._name
199+ class Person :
200+ name = Name()
201+ ```
202+ 203+ 204+ # Deskryptory a klasy osadzone
205+ 206+ ``` python
207+ class A :
208+ class B :
209+ def __get__ (* args ): return 1234
210+ a = B()
211+ ```
212+ 213+ 214+ # Informacja o stanie w deskryptorze
215+ 216+ ``` python
217+ class B :
218+ def __init__ (self
219+ self .cnt = 0
220+ def __get__ (* args ):
221+ self .cnt += 1
222+ print (self .cnt)
223+ return 1234
224+ class A :
225+ a = B()
226+ x = A()
227+ x.a # 1 1234
228+ x.a # 2 1234
229+ ```
230+ 231+ 232+ # Metody getattr oraz getattribute
233+ 234+ Różnica:
235+ 236+ - metoda _ getattr_ : niezdefiniowane atrybuty
237+ - metoda _ getattribute_ : każdy atrybut
238+ 239+ 240+ 241+ # Zarządzanie atrybutami
242+ 243+ ``` python
244+ def __getattr__ (self name ) # niezdefiniowane
245+ def __getattribute__ (self name ) # wszystkie
246+ def __setattr__ (self name , value ) # wszystkie
247+ def __delattr__ (self name ) # wszystkie
248+ ```
249+ 250+ 251+ # Zarządzane atrybuty
252+ 253+ ``` python
254+ class Wrapper :
255+ def __init__ (self object ):
256+ self .wrapped = object
257+ def __getattr__ (self attrname ):
258+ print (' Śledzenie: ' + attrname)
259+ return getattr (self .wrapped, attrname)
260+ ```
261+ 262+ 263+ 264+ # Zagadka
265+ 266+ ``` python
267+ class A :
268+ def __getattribute__ (self name ):
269+ return self .other
270+ x = A()
271+ print (x.abc)
272+ ```
273+ 274+ 275+ # Zagadka - rozwiązanie
276+ 277+ ``` python
278+ RecursionError !
279+ ```
280+ 281+ 282+ 283+ # Zagadka - kod
284+ 285+ ``` python
286+ class A :
287+ def __getattribute__ (self name ):
288+ return object .__getattribute__ (self , ' other'
289+ ```
290+ 291+ 292+ 293+ # Pętla nr 2
294+ 295+ ``` python
296+ class A :
297+ def __setattr__ (self attrname , value ):
298+ self .other = value # pętla!
299+ ```
300+ 301+ 302+ # Pętla nr 2 - rozwiązanie
303+ 304+ ``` python
305+ class A :
306+ def __setattr__ (self attrname , value ):
307+ self .__dict__ [' other' = value
308+ ```
309+ 310+ 311+ # Pętla nr 1 - CD
312+ 313+ ``` python
314+ class A :
315+ def __getattribute__ (self attrname ):
316+ return self .__dict__ [attrname] # ?
317+ ```
318+ 319+
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