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CS2613 Assignment 4
Posted Tags: /tags/python
Lab 19

Before the lab

Read

Getting started

Generators and iterator classes

Time
25 minutes
Activity
individual

Consider the countdown generator from Section 6.2

def countdown(n):
    print('Counting down from', n)
    while n > 0:
        yield n
        n -= 1

Referring to Section 6.1 an equivalent iterator class. Here we will implement the entire protocol with one class, but multiple classes like we did for JavaScript is also reasonable. Modify only the __next__ method of the following skeleton class so that given tests pass.

def countdown(n):
    yield 'starting'
    while n > 0:
        yield n
        n -= 1

def test_generator():
    counter = countdown(3)
    assert [ t for t in counter ] == \
        ['starting', 3,  2,  1]

class Counter:
    "Iterator class simulating countdown"
    def __init__(self,n):
        self.n = n
        self.first = True

    def __iter__(self):
        return self
    
    def __next__(self):
        # insert code here
        self.n -= 1
        return self.n+1

def test_class():
    counter = Counter(3)
    assert [ t for t in counter ] == \
        ['starting', 3,  2,  1]

What is __iter__ for?

Time
25 minutes
Activity
individual

Update the __iter__ method of your previous solution so that the following additional test passes

def test_twice():
    counter = Counter(3)
    assert [ t for t in counter ] == \
        ['starting', 3,  2,  1]
    assert [ t for t in counter ] == \
        ['starting', 3,  2,  1]

Using Generators I

Time
25 minutes
Activity
individual

Do Exercises 6.5 and 6.6.

Note that 6.5 just asks you to run some code, but you do have to be in the correct directory when running it.

For 6.6, you essentially need to split the given code so that the first part is the new generator follow.

Using Generators II

Time
25 minutes
Activity
individual

Start with the following stock related classes:

portfolio.py

fileparse.py

report.py

stock.py

tableformat.py

Complete Exercise 6.7. I suggest you make a new file follow2.py so that you preserve solutions for 6.6 and 6.7.

Posted Tags: /tags/python
JS Quiz / Lab 18

Before the Lab

Study for the JavaScript Quiz

Read

Quiz

Time
50 minutes
Activity
Quiz

The first half of the lab will be a javascript quiz

Getting started

Static methods

Time
25 minutes
Activity
Transform code, use template for static methods
    @staticmethod
    def read_portfolio(filename):
        # code from 4.3 goes here

Your completed static method should pass

def test_read_portfolio():
    portfolio = Stock.read_portfolio('Data/portfolio.csv')
    assert repr(portfolio[0:3]) == \
        "[Stock('AA', 100, 32.2), Stock('IBM', 50, 91.1), Stock('CAT', 150, 83.44)]"

Inheritance

Time
25 minutes
Activity
Refactor given code, work with class hierarchy

Start with following class hierarchy based on Exercises 4.5 and 4.6

class TableFormatter:
    def headings(self, headers):
        '''
        Emit the table headings.
        '''
        raise NotImplementedError()

    def row(self, rowdata):
        '''
        Emit a single row of table data.
        '''
        raise NotImplementedError()

class TextTableFormatter(TableFormatter):
    '''
    Emit a table in plain-text format
    '''
    def headings(self, headers):
        
        output = ''
        for h in headers:
            output += f'{h:>10s} '
        output+='\n'
        output+=(('-'*10 + ' ')*len(headers))
        output += '\n'
        return output
    
    def row(self, rowdata):
        output = ''
        for d in rowdata:
            output+=f'{d:>10s} '
        output += '\n'
        return output

def test_text_2():
    portfolio=stock.Stock.read_portfolio('Data/portfolio.csv')
    formatter= TextTableFormatter()
    output= formatter.headings(['Name','Shares','Price', 'Cost'])
    for obj in portfolio[0:3]:
        output +=formatter.row([obj.name,f'{obj.shares}',
                                f'{obj.price:0.2f}',f'{obj.cost():0.2f}'])

    assert '\n' + output == '''
      Name     Shares      Price       Cost 
---------- ---------- ---------- ---------- 
        AA        100      32.20    3220.00 
       IBM         50      91.10    4555.00 
       CAT        150      83.44   12516.00 
'''

 
def test_string_1():
    portfolio=stock.Stock.read_portfolio('Data/portfolio.csv')
    formatter= StockTableFormatter()
    output= formatter.headings(['Name','Shares','Price', 'Cost'])
    for obj in portfolio[0:3]:
        output +=formatter.row(obj)

    assert '\n' + output == '''
      Name     Shares      Price       Cost 
---------- ---------- ---------- ---------- 
        AA        100      32.20    3220.00 
       IBM         50      91.10    4555.00 
       CAT        150      83.44   12516.00 
'''

Before next lab

Study for the JavaScript Quiz

Read

Posted Tags: /tags/python
Lab 17

Before the Lab

Read

Getting started

Questions

Time
10 minutes
Activity
Add error check

Raising exceptions

Time
20 minutes
Activity
Add error check
def test_exception():
    with pytest.raises(RuntimeError) as e_info:
        prices = parse_csv('Data/prices.csv', select=['name','price'], has_headers=False)

Modules

Time
20 minutes
Activity
Refactor existing code to to reuse a function.
def test_prices():
    portfolio = read_portfolio('Data/portfolio.csv')

    prices = {  s['name']: s['price'] for s in portfolio }
    assert prices['AA'] == pytest.approx(32.2,abs=0.001)
    assert prices['GE'] == pytest.approx(40.37,abs=0.001)

Methods

Time
25 minutes
Activity
Write accessor and mutator methods.

def test_cost2():
    s = Stock('GOOG', 100, 490.10)
    assert s.cost() == pytest.approx(49010.0,0.001)

def test_sell():
    s = Stock('GOOG', 100, 490.10)
    s.sell(25)
    assert s.shares == 75
    assert s.cost() == pytest.approx(36757.5, 0.001)

Special Methods

Time
25 minutes
Activity
Code to test, learn about "dunder" methods.
def test_repr():
    goog = Stock('GOOG', 100, 490.1)
    assert repr(goog) == "Stock('GOOG', 100, 490.1)"

Before next lab

Study for the JavaScript Quiz

Read

Posted Tags: /tags/python
Lab 16

Before the Lab

Read

Getting Started

Sequences

Time
25 minutes
Activity
Convert REPL session to tests
def test_items():
    assert prices.items() == \
        [('GOOG', 490.1), ('AA', 23.45), ('IBM', 91.1), ('MSFT', 34.23)]

- Question for your journal: what is `list()` being used for in this section?
- Embed the following tests and make sure they pass

def test_zip():
    assert pricelist == \
        [(490.1, 'GOOG'), (23.45, 'AA'), (91.1, 'IBM'), (34.23, 'MSFT')]

def test_min_max():
    assert min(pricelist) == (23.45, 'AA')
    assert max(pricelist) == (490.1, 'GOOG')

List Comprehensions

Time
25 minutes
Activity
Write tests based on REPL session
import pytest
from report2 import read_portfolio
prices = {
        'GOOG' : 490.1,
        'AA' : 23.45,
        'CAT': 35.46,
        'IBM' : 91.1,
        'MSFT' : 34.23,
        'GE': 13.48,
    }

Note that the value test will need to be adjusted for a value of approximately 31167.10, since our price list is different from the one used in the book.

Higher order functions

Time
20 minutes
Activity
Assemble given pieces
def test_portfolio():
    portfolio = parse_csv('Data/portfolio.csv', types=[str, int, float])
    assert portfolio == [{'price': 32.2, 'name': 'AA', 'shares': 100},
                         {'price': 91.1, 'name': 'IBM', 'shares': 50},
                         {'price': 83.44, 'name': 'CAT', 'shares': 150},
                         {'price': 51.23, 'name': 'MSFT', 'shares': 200},
                         {'price': 40.37, 'name': 'GE', 'shares': 95},
                         {'price': 65.1, 'name': 'MSFT', 'shares': 50},
                         {'price': 70.44, 'name': 'IBM', 'shares': 100}]

def test_shares():
    shares_held = parse_csv('Data/portfolio.csv', select=['name', 'shares'], types=[str, int])
    assert shares_held == [{'name': 'AA', 'shares': 100}, {'name': 'IBM', 'shares': 50},
                           {'name': 'CAT', 'shares': 150}, {'name': 'MSFT', 'shares': 200},
                           {'name': 'GE', 'shares': 95}, {'name': 'MSFT', 'shares': 50},
                           {'name': 'IBM', 'shares': 100}]

Refactoring a function

Time
30 minutes
Activity
Refactor function to add feature
def test_tuple():
    prices = parse_csv('Data/prices.csv', types=[str,float], has_headers=False)
    assert prices == [('AA', 9.22), ('AXP', 24.85), ('BA', 44.85), ('BAC', 11.27),
                      ('C', 3.72), ('CAT', 35.46), ('CVX', 66.67), ('DD', 28.47),
                      ('DIS', 24.22), ('GE', 13.48), ('GM', 0.75), ('HD', 23.16),
                      ('HPQ', 34.35), ('IBM', 106.28), ('INTC', 15.72), ('JNJ', 55.16),
                      ('JPM', 36.9), ('KFT', 26.11), ('KO', 49.16), ('MCD', 58.99),
                      ('MMM', 57.1), ('MRK', 27.58), ('MSFT', 20.89), ('PFE', 15.19),
                      ('PG', 51.94), ('T', 24.79), ('UTX', 52.61), ('VZ', 29.26),
                      ('WMT', 49.74), ('XOM', 69.35)]
Posted Tags: /tags/python
Lab 15

Before the Lab

Read

Getting Started

Files

Time
20 minutes
Activity
Individual programming, synthesis

Data types

Tuples

Time
20 minutes
Activity
Individual programming, synthesis

Dictionaries

Time
20 minutes
Activity
Individual programming, synthesis
def test_cost():
    d = parse_row(row)
    cost = compute_cost (d)
    assert cost == pytest.approx(3220.000,abs=0.00000001)

def test_d():
    d = parse_row(row)
    update_dict(d)
    assert d == {'name': 'AA', 'shares': 75, 'price':32.2, 'date': (6, 11, 2007),
                 'account': 12345}

Containers: read_portfolio

Time
20 minutes
Activity
Write function based on template
def test_read():
    portfolio = read_portfolio('Data/portfolio.csv')
    assert portfolio == \
        [('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)]

def test_total():
    portfolio = read_portfolio('Data/portfolio.csv')
    total = 0.0
    for name, shares, price in portfolio:
        total += shares*price
    assert total == pytest.approx(44671.15,abs=0.001)
Time
20 minutes
Activity
Modify results of previous exercise
def test_read():
    portfolio = read_portfolio('Data/portfolio.csv')
    assert portfolio == \
        [{'name': 'AA', 'shares': 100, 'price': 32.2}, {'name': 'IBM', 'shares': 50, 'price': 91.1},
         {'name': 'CAT', 'shares': 150, 'price': 83.44}, {'name': 'MSFT', 'shares': 200, 'price': 51.23},
         {'name': 'GE', 'shares': 95, 'price': 40.37}, {'name': 'MSFT', 'shares': 50, 'price': 65.1},
         {'name': 'IBM', 'shares': 100, 'price': 70.44}]

def test_total():
    portfolio = read_portfolio('Data/portfolio.csv')

    total = 0.0
    for s in portfolio:
        total += s['shares']*s['price']
    assert total == pytest.approx(44671.15,abs=0.001)

Before next lab

Read

Posted Tags: /tags/python
Lab 14

Before the Lab

Questions

Time
5 Minutes
Activity
Group discussion

Getting Started

Mortgage Calculator

Time
20 Minutes
Activity
Modify given program

Do exercises 1.7 and 1.8 from Python Numbers

Introduction to Python strings

Time
20 Minutes
Activity
Experiment in Python REPL

Do exercises 1.13, 1.14, 1.15 from Python Strings

Pytest

Time
10 minutes
Activity
Demo
symbols = 'HPQ,AAPL,IBM,MSFT,YHOO,DOA,GOOG'
symlist = symbols.split(',')

def test_lookup0():
    assert symlist[0] == 'HPQ'

def test_lookup1():
    assert symlist[1] == 'AAPL'

[student@id414m22 L14]$ pytest listex.py
=================== test session starts ===================
platform linux -- Python 3.9.18, pytest-7.4.3, pluggy-1.3.0
rootdir: /home1/ugrad/student/cs2613/labs/L14
plugins: pylama-8.4.1, cov-4.1.0
collected 2 items

listex.py ..                                        [100%]

==================== 2 passed in 0.02s ====================

Lists and Pytest

Time
20 minutes
Activity
Individual programming from template

Functions and coverage

Time
20 minutes
Activity
Individual programming, modify previous solution

We have already been using python functions for pytest, without really thinking about how they work. In Part 1.7 of Practical Python, functions are explained.

def sumcount(n):
    '''
    Returns the sum of the first n integers
    '''
    total = 0
    while n > 0:
        total += n
        n -= 1
    return total

Before next lab

Read

Posted Tags: /tags/python
Indexing Debian's buildinfo

Introduction

Debian is currently collecting buildinfo but they are not very conveniently searchable. Eventually Chris Lamb's buildinfo.debian.net may solve this problem, but in the mean time, I decided to see how practical indexing the full set of buildinfo files is with sqlite.

Hack

  1. First you need a copy of the buildinfo files. This is currently about 2.6G, and unfortunately you need to be a debian developer to fetch it.

     $ rsync -avz mirror.ftp-master.debian.org:/srv/ftp-master.debian.org/buildinfo .

  2. Indexing takes about 15 minutes on my 5 year old machine (with an SSD). If you index all dependencies, you get a database of about 4G, probably because of my natural genius for database design. Restricting to debhelper and dh-elpa, it's about 17M.

     $ python3 index.py

    You need at least python3-debian installed

  3. Now you can do queries like

     $ sqlite3 depends.sqlite "select * from depends where depend='dh-elpa' and depend_version<='0106'"

    where 0106 is some adhoc normalization of 1.6

Conclusions

The version number hackery is pretty fragile, but good enough for my current purposes. A more serious limitation is that I don't currently have a nice (and you see how generous my definition of nice is) way of limiting to builds currently available e.g. in Debian unstable.

Posted Tags: /tags/python
Trivial example using python to hack ical

I could not find any nice examples of using the vobject class to filter an icalendar file. Here is what I got to work. I'm sure there is a nicer way. This strips all of the valarm subevents (reminders) from an icalendar file.

import vobject
import sys

cal=vobject.readOne(sys.stdin)

for ev in cal.vevent_list:
    if ev.contents.has_key(u'valarm'):
       del ev.contents[u'valarm']

print cal.serialize()
Posted Tags: /tags/python