coding-mentor-agent/kb/python-course-kb-practical-python/wiki/exercises/4-10-an-example-of-using-getattr.md

id, source_exercise_id, title, section, source_path, source_repo, source_commit, student_visible_solution, has_private_solution, skip

id	source_exercise_id	title	section	source_path	source_repo	source_commit	student_visible_solution	has_private_solution	skip
practical-python-4.10	4.10	An example of using getattr()	4.3 Special Methods	04_Classes_objects/03_Special_methods.md	https://github.com/dabeaz-course/practical-python	93dca856b41c61a0a0f85ae334116e4c125629ea	false	true	false

Exercise 4.10: An example of using getattr()

Source: Practical Python Programming, 04_Classes_objects/03_Special_methods.md.

Exercise 4.10: An example of using getattr()

getattr() is an alternative mechanism for reading attributes. It can be used to write extremely flexible code. To begin, try this example:

>>> import stock
>>> s = stock.Stock('GOOG', 100, 490.1)
>>> columns = ['name', 'shares']
>>> for colname in columns:
        print(colname, '=', getattr(s, colname))

name = GOOG
shares = 100
>>>

Carefully observe that the output data is determined entirely by the attribute names listed in the columns variable.

In the file tableformat.py, take this idea and expand it into a generalized function print_table() that prints a table showing user-specified attributes of a list of arbitrary objects. As with the earlier print_report() function, print_table() should also accept a TableFormatter instance to control the output format. Here's how it should work:

>>> import report
>>> portfolio = report.read_portfolio('Data/portfolio.csv')
>>> from tableformat import create_formatter, print_table
>>> formatter = create_formatter('txt')
>>> print_table(portfolio, ['name','shares'], formatter)
      name     shares
---------- ----------
        AA        100
       IBM         50
       CAT        150
      MSFT        200
        GE         95
      MSFT         50
       IBM        100

>>> print_table(portfolio, ['name','shares','price'], formatter)
      name     shares      price
---------- ---------- ----------
        AA        100       32.2
       IBM         50       91.1
       CAT        150      83.44
      MSFT        200      51.23
        GE         95      40.37
      MSFT         50       65.1
       IBM        100      70.44
>>>

Contents | Previous (4.2 Inheritance) | Next (4.4 Exceptions)

关联来源

• summaries/03_Special_methods