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A D Vishnu Prasad
2020-05-29 19:15:25 +05:30
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Notes/04_Classes_objects/02_Inheritance.md
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@@ -1,4 +1,4 @@
[Contents](../Contents) \| [Previous (4.1 Classes)](01_Class) \| [Next (4.3 Special methods)](03_Special_methods)
[Contents](../Contents.md) \| [Previous (4.1 Classes)](01_Class) \| [Next (4.3 Special methods)](03_Special_methods)
# 4.2 Inheritance
@@ -158,7 +158,7 @@ class Rectangle(Shape):
```
Think of a logical hierarchy or taxonomy. However, a more common (and
practical) usage is related to making reusable or extensible code.
practical) usage is related to making reusable or extensible code.
For example, a framework might define a base class and instruct you
to customize it.
@@ -170,7 +170,7 @@ class CustomHandler(TCPHandler):
```
The base class contains some general purpose code.
Your class inherits and customized specific parts.
Your class inherits and customized specific parts.
### "is a" relationship
@@ -193,7 +193,7 @@ True
>>>
```
*Important: Ideally, any code that worked with instances of the parent
*Important: Ideally, any code that worked with instances of the parent
class will also work with instances of the child class.*
### `object` base class
@@ -235,7 +235,7 @@ going to utilize multiple inheritance further in this course.
A major use of inheritance is in writing code that's meant to be
extended or customized in various ways--especially in libraries or
frameworks. To illustrate, consider the `print_report()` function
frameworks. To illustrate, consider the `print_report()` function
in your `report.py` program. It should look something like this:
```python
@@ -298,7 +298,7 @@ class TableFormatter:
raise NotImplementedError()
```
This class does nothing, but it serves as a kind of design specification for
This class does nothing, but it serves as a kind of design specification for
additional classes that will be defined shortly. A class like this is
sometimes called an "abstract base class."
@@ -334,7 +334,7 @@ def portfolio_report(portfoliofile, pricefile):
'''
Make a stock report given portfolio and price data files.
'''
# Read data files
# Read data files
portfolio = read_portfolio(portfoliofile)
prices = read_prices(pricefile)
@@ -355,7 +355,7 @@ Run this new code:
... crashes ...
```
It should immediately crash with a `NotImplementedError` exception. That's not
It should immediately crash with a `NotImplementedError` exception. That's not
too exciting, but it's exactly what we expected. Continue to the next part.
### Exercise 4.6: Using Inheritance to Produce Different Output
@@ -392,7 +392,7 @@ def portfolio_report(portfoliofile, pricefile):
'''
Make a stock report given portfolio and price data files.
'''
# Read data files
# Read data files
portfolio = read_portfolio(portfoliofile)
prices = read_prices(pricefile)
@@ -446,7 +446,7 @@ def portfolio_report(portfoliofile, pricefile):
'''
Make a stock report given portfolio and price data files.
'''
# Read data files
# Read data files
portfolio = read_portfolio(portfoliofile)
prices = read_prices(pricefile)
@@ -494,7 +494,7 @@ Test your code by modifying the main program to create a
### Exercise 4.7: Polymorphism in Action
A major feature of object-oriented programming is that you can
A major feature of object-oriented programming is that you can
plug an object into a program and it will work without having to
change any of the existing code. For example, if you wrote a program
that expected to use a `TableFormatter` object, it would work no
@@ -512,7 +512,7 @@ def portfolio_report(portfoliofile, pricefile, fmt='txt'):
'''
Make a stock report given portfolio and price data files.
'''
# Read data files
# Read data files
portfolio = read_portfolio(portfoliofile)
prices = read_prices(pricefile)
@@ -547,7 +547,7 @@ def portfolio_report(portfoliofile, pricefile, fmt='txt'):
'''
Make a stock report given portfolio and price data files.
'''
# Read data files
# Read data files
portfolio = read_portfolio(portfoliofile)
prices = read_prices(pricefile)
@@ -568,15 +568,15 @@ an optional argument specifying the output format. For example:
```python
>>> report.portfolio_report('Data/portfolio.csv', 'Data/prices.csv', 'txt')
Name Shares Price Change
---------- ---------- ---------- ----------
AA 100 9.22 -22.98
IBM 50 106.28 15.18
CAT 150 35.46 -47.98
MSFT 200 20.89 -30.34
GE 95 13.48 -26.89
MSFT 50 20.89 -44.21
IBM 100 106.28 35.84
Name Shares Price Change
---------- ---------- ---------- ----------
AA 100 9.22 -22.98
IBM 50 106.28 15.18
CAT 150 35.46 -47.98
MSFT 200 20.89 -30.34
GE 95 13.48 -26.89
MSFT 50 20.89 -44.21
IBM 100 106.28 35.84
>>>
```
@@ -614,7 +614,7 @@ you can change the internal implementation to work in any way that you
want. You can write all-custom code. You can use someone's third
party package. You swap out one third-party package for a different
package when you find a better one. It doesn't matter--none of
your application code will break as long as you preserve keep the
your application code will break as long as you preserve keep the
interface. That's a powerful idea and it's one of the reasons why
you might consider inheritance for something like this.
@@ -624,4 +624,4 @@ on the topic of design patterns (although understanding what happened
in this exercise will take you pretty far in terms of using objects in
a practically useful way).
[Contents](../Contents) \| [Previous (4.1 Classes)](01_Class) \| [Next (4.3 Special methods)](03_Special_methods)
[Contents](../Contents.md) \| [Previous (4.1 Classes)](01_Class) \| [Next (4.3 Special methods)](03_Special_methods)