Khi thiết lập hướng đối tượng với Python, ta thường bắt gặp các câu lệnh như
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
0 hoặc class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
1 nhất là khi đọc tài liệu của các thư viện có các lớp kế thừa nhiều lần. Bài viết hôm nay của mình sẽ hướng đến giới thiệu hàm class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
2 và các trường hợp sử dụng nó1. Kế thừa trong Python
Để hiểu rõ hơn về vai trò của
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
2. Mình sẽ bắt đầu với trường hợp không sử dụng class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
2 trong kế thừa trước. Cho lớp cha class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
5 và được kế thừa bởi lớp con class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
6, khi đó lớp class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
7 có thể gọi các phương thức hoặc thuộc tính từ lớp cha________số 8Tuy nhiên, sẽ xảy ra trường hợp
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
7 và class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
5 có phương thức trùng tên với nhau là class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
10 và ta cần gọi phương thức class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
10 của class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
5 bên trong phương thức class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
13 của class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
7. Trường hợp này vẫn có thể được giải quyết mà không cần sử dụng đến class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
2 bằng cách gọi trực tiếp class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
16 bên trong class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
17class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
9Nhiều bạn đã biết về phương thức ràng buộc, phương thức không ràng buộc có thể sẽ thắc mắc tại sao lại sử dụng tham số
18 cho phương thứcclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
10 dù hàm này không sử dụng thuộc tính hay phương thức củaclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
18. Vì mình muốn tập trung vào giới thiệu phương pháp kế thừa nên đã viết đơn giản hơn vì có thêm decorator và thay đổi cách gọi hàm. Bạn nào có nhu cầu tìm hiểu thêm về phương pháp có ràng buộc, phương pháp không có ràng buộc có thể tham khảo tại đâyclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
Chúng ta cũng có thể giải quyết trường hợp này bằng cách sử dụng
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
2 thay vì gọi trực tiếpclass Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
Hàm
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
2 lúc này sẽ trả về một đối tượng thuộc lớp kế thừa từ class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
7 lúc này là class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
5 và gọi là class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
85. Khác với cách gọi trực tiếp, class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
2 không cần viết lại tên lớp class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
5 khi gọi hàm, công việc này sẽ giúp tránh các lỗi mô tả chính xác hoặc bạn có nhu cầu đổi tên lớp cha hoặc kế thừa từ lớp khác. Nhưng đấy vẫn chưa phải là tất cả điểm mạnh của
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
2. class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
2 được sử dụng linh hoạt trong các trường hợp đa kế thừa đặc biệt là mà mình sẽ giới thiệu sau đây. Trước hết chúng ta cần phải hiểu rõ một vài khái niệm và các tham số của class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
22. Thứ tự giải quyết phương pháp [MRO]
MRO có thể hiểu đơn giản là trình tự kế thừa của lớp. MRO của một lớp có thể được truy xuất bằng phương thức
MRO sẽ được tạo để đảm bảo các lớp chỉ được liệt kê một lần và các lớp con phải được gọi trước lớp cha. Nếu bạn muốn tìm hiểu thêm về thuật toán tạo MRO của Python thì tham khảo tại đây
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
1Khi sử dụng một phương thức với các đối tượng thuộc Lớp con, chương trình sẽ tìm kiếm phương thức dựa trên thứ tự MRO như trên, tức là bắt đầu từ Lớp con, nếu không có thì tìm kiếm sẽ đến Lớp cha và sau cùng là [lớp cơ sở
3. Tham số của hàm class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
2
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
Hàm
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
63 sẽ nhận vào hai tham số class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
64 và class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
65
64 sẽ nhận giá trị kiểu lớp để khi tìm kiếm phương thức hoặc thuộc tính, chương trình sẽ tìm các lớp cha sauclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
64 trong MRO của lớp. dựa vàoclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
64 ta có thể quyết định phương thức cần gọi được cài đặt trong Lớp cha hoặc Lớp ông nộiclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
65 sẽ nhận vào một đối tượng để ràng buộc [ràng buộc] với phương thức hoặc thuộc tính được gọi bởiclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
2class Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
Để dễ hình dung,
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
41 có thể hiểu là class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
42 với phương thức class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
43 được cài đặt trong lớp cha của class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
64Các ví dụ trên, hàm
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
2 được gọi trong lớp class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
7 sẽ có giá trị tham số mặc định là class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
47class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
8Ngoài
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
64 và class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
65 còn có một số ràng buộc để chương trình chạy không bị lỗi mà bạn có thể tham khảo tại của class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
2Lưu ý. If in ________ 551 of layer ________ 552 call next ________ 553. Hàm sẽ tìm thấy
51 của các lớp phía sau lớpclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
52 trong MRO. Ở đây MRO sẽ làclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
56, vìclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
65 không được cài đặtclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
51 nên sẽ trả về lỗiclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
59class Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
4. Giải quyết Vấn đề kim cương bằng super[]
Sự cố kim cương xuất hiện khi ta thực hiện đa kế thừa trên hai lớp cha cùng kế thừa từ một lớp nội.
Xét trường hợp ta có các lớp sau.
- Lớp
52class Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
- Lớp
51 và lớpclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
52 cùng kế thừa từ lớpclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
53class Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
- Lớp
54 đa kế thừa từ hai lớpclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
55 vàclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
56class Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
Khi đó chúng ta sẽ gặp các vấn đề phát sinh sau
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
55 và class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
56 có trùng tên nhauNếu bạn gọi phương thức bằng
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
2, phương thức của lớp có thứ tự nhỏ hơn trong MRO sẽ được gọi trước. Trong trường hợp này, lớp cha thứ tự trong MRO sẽ là thứ tự liệt kê lớp cha trong lúc khai báo Lớp class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
7class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
6Nếu muốn gọi
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
51 của class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
56 ta có thể làm như sau- Change thứ tự báo cáo
83class Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
- Call direct
84class Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
Phương thức của lớp
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
52 được gọi lại hai lầnVấn đề này gặp phải khi chúng ta muốn gọi phương thức khởi tạo của
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
55 và class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
56 trực tiếp bên trong class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
7, nhưng phương thức khởi tạo của class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
55 và class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
56 lại gọi lại phương thức khởi tạo của class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
53. Khi đó sẽ xảy ra việc phương thức khởi tạo của class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
53 bị gọi 2 lầnclass Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
4Cách giải quyết. use function
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
2 instead of call direct. Như đã lưu ý ở mục 3. hàm class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
2 sẽ tìm các phương thức khởi tạo dựa trên MRO và lớp hiện tại. Vì các lớp chỉ xuất hiện trong MRO duy nhất một lần nên khi gọi class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
0 sẽ tránh được cuộc gọi nhiều lần, giảm thiểu thời gian chạy và tránh bị ghi không cần thiếtclass Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
5Tuy nhiên, điều này lại dẫn đến vấn đề sau
Phương thức khởi tạo của
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
55 và class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
56 cần có các tham số khác nhauGiả sử ta cần lưu số tuổi của mỗi lớp thông qua các biến
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
908, class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
909, class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
910 và class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
911< . Xét đoạn code sau đây:
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
5Mỗi lớp đều cần tham số khác nhau khi khởi động nên theo thứ tự MRO đã biết trước, chúng ta có thể viết mã như trên. Tuy code chạy đúng như ý muốn nhưng mình tin ảo ai muốn code as on vì các lý do sau
- Sai bản chất. ngoại trừ khi
55 vàclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
56 chỉ được khởi động đúng một lần và chỉ sử dụng để tạo lớpclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
7, với mã trên khi tạo đối tượng thuộc lớpclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
55 hoặcclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
56 sẽ bị lỗi dư tham sốclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
- Reshard hard. Vì tham số truyền vào
917 dựa trên MRO nên sẽ phụ thuộc thứ tự khai báo của lớp, chỉ cần thay đổi thứ tự lại là có thể làm cho mã chạy bị lỗiclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
- Khó tái sử dụng. Giả sử như chúng ta có thêm lớp
918 và muốn tạo lớp đa kế thừa từclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
55 vàclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
918. Khi đó ta phải viết lạiclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
917 củaclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
55 để đa kế thừa, điều này có thể ảnh hưởng đến lớpclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
7 hiện tạiclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
Cách giải quyết. used
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
924 in class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
917. Khi đó chúng ta cần phải thiết kế lại tất cả các phương thức class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
917 của tất cả các lớpclass Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
8Mã vẫn trả về kết quả như ý nhưng gọn hơn và dễ bảo trì, mở rộng hơn
Chúng ta vẫn có thể giải quyết trường hợp này bằng cách gọi phương thức khởi tạo trực tiếp nếu bạn chắc chắn không bị ghi đè lên lớp
class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
52 hoặc ghi đè không gây ảnh hưởng gì [nhưng mình vẫn hoan nghênh việc sử dụng class Children[Parent]:
def self_intro[self]:
print["This is children class"]
def family_intro[self]:
self.self_intro[] # Same as Children.self_intro[self]
super[].self_intro[]
c = Children[]
c.family_intro[]
# >>> This is children class
# >>> This is parent class
2 hơn vì . ]5. Kết bài
Qua bài này mình đã trình bày với các bạn
- Call the method from layer cha by
2 or direct nextclass Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
- MRO MRO và ý nghĩa tham số của
2class Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
- Vấn đề kim cương và cách giải quyết bằng
2class Children[Parent]: def self_intro[self]: print["This is children class"] def family_intro[self]: self.self_intro[] # Same as Children.self_intro[self] super[].self_intro[] c = Children[] c.family_intro[] # >>> This is children class # >>> This is parent class
Nếu bài viết có chỗ nào không rõ hoặc sai thì xin hãy cho mình biết. Cảm ơn các bạn đã dành thời gian đọc bài viết này