Chain of Responsibility Design Pattern
Videos
| Section | Video Links |
|---|---|
| Chain of Responsibility |    |
| Use Case | |
| Python Floor Division | |
| Accepting User Input | |
Book
Overview
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Terminology
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Chain of Responsibility UML Diagram
Source Code
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Output
python ./chain_of_responsibility/chain_of_responsibility_concept.py Successor1 payload = 1 Successor2 payload = -1 Successor2 payload = -0.5 Successor2 payload = -0.25 Successor1 payload = -0.5 Successor1 payload = 0.5 Successor2 payload = -1.5 Finished result = -1.5
Example Use Case
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Example UML Diagram
Output
python ./chain_of_responsibility/client.py
Enter amount to withdrawal : 180
Dispensing 3 £50 note(s)
Dispensing 1 £20 note(s)
Dispensing 1 £10 note
Now go spoil yourselfNew Coding Concepts
Floor Division
Normally division uses a single / character and will return a float even if the numbers are integers or exactly divisible with no remainder,
E.g.,
Python Version 3 also has an option to return an integer version (floor) of the number by using the double // characters instead.
See PEP-0238 : https://www.python.org/dev/peps/pep-0238/
Accepting User Input
In the file /chain_of_responsibility/client.py above, there is a command input .
The input command allows your script to accept user input from the command prompt.
In the ATM example, when you start it, it will ask the user to enter a number.
Then when the user presses the enter key, the input is converted to an integer and the value tested if valid.
AMOUNT = int(input("Enter amount to withdrawal : ")) if AMOUNT < 10 or AMOUNT % 10 != 0: ...continue
Note that in Python 2.x, use the raw_input() command instead of input() .
See PEP-3111 : https://www.python.org/dev/peps/pep-3111/
Summary
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