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Exercises/ex3_1.md

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+\[ [Index](index.md) | [Exercise 2.6](ex2_6.md) | [Exercise 3.2](ex3_2.md) \]
+
+# Exercise 3.1
+
+*Objectives:*
+
+- Define a simple class
+
+*Files Modified:* `stock.py`
+
+In link:ex1_5.html[Exercise 1.5], you defined a simple class
+`Stock` for representing a holding of stock.  In this exercise,
+we're simply going to add a few features to that class as well as
+write some utility functions.
+
+## (a) Adding a new method
+
+Add a new method `sell(nshares)` to Stock that sells a certain number
+of shares by decrementing the share count.  Have it work like this:
+
+```python
+>>> s = Stock('GOOG',100,490.10)
+>>> s.shares
+100
+>>> s.sell(25)
+>>> s.shares
+75
+>>>
+```
+
+## (b) Reading a portfolio
+
+Add a function `read_portfolio()` to your `stock.py` program that
+reads a file of portfolio data into a list of `Stock` objects. Here's how it should work:
+
+```python
+>>> portfolio = read_portfolio('Data/portfolio.csv')
+>>> for s in portfolio:
+        print(s)
+
+<__main__.Stock object at 0x3902f0>
+<__main__.Stock object at 0x390270>
+<__main__.Stock object at 0x390330>
+<__main__.Stock object at 0x390370>
+<__main__.Stock object at 0x3903b0>
+<__main__.Stock object at 0x3903f0>
+<__main__.Stock object at 0x390430>
+>>>
+```
+
+You already wrote a similar function as part of
+link:ex2_3.html[Exercise 2.3].  Design discussion: Should
+`read_portfolio()` be a separate function or part of the class
+definition?
+
+## (c) Printing a Table
+
+Table the data read in part (b) and use it to make a nicely formatted
+table. For example:
+
+```python
+>>> portfolio = read_portfolio('Data/portfolio.csv')
+>>> for s in portfolio:
+           print('%10s %10d %10.2f' % (s.name, s.shares, s.price))
+
+        AA        100      32.20
+       IBM         50      91.10
+       CAT        150      83.44
+      MSFT        200      51.23
+        GE         95      40.37
+      MSFT         50      65.10
+       IBM        100      70.44
+>>>
+```
+
+Take this code and put it in a function `print_portfolio()` that 
+produces the same output, but additionally adds some table headers.
+For example:
+
+```python
+>>> portfolio = read_portfolio('Data/portfolio.csv')
+>>> print_portfolio(portfolio)
+      name     shares      price
+---------- ---------- ---------- 
+        AA        100      32.20
+       IBM         50      91.10
+       CAT        150      83.44
+      MSFT        200      51.23
+        GE         95      40.37
+      MSFT         50      65.10
+       IBM        100      70.44
+>>>
+```
+
+\[ [Solution](soln3_1.md) | [Index](index.md) | [Exercise 2.6](ex2_6.md) | [Exercise 3.2](ex3_2.md) \]
+
+----
+`>>>` Advanced Python Mastery  
+`...` A course by [dabeaz](https://www.dabeaz.com)  
+`...` Copyright 2007-2023  
+
+![](https://i.creativecommons.org/l/by-sa/4.0/88x31.png). This work is licensed under a [Creative Commons Attribution-ShareAlike 4.0 International License](http://creativecommons.org/licenses/by-sa/4.0/)