Python basic programs-2
11 lines: Triple-quoted
strings, while loop
REFRAIN = '''
%d bottles of beer on the wall,
%d bottles of beer,
take one down, pass it around,
%d bottles of beer on the wall!
'''
bottles_of_beer = 99
while bottles_of_beer > 1:
print REFRAIN % (bottles_of_beer, bottles_of_beer,
bottles_of_beer - 1)
bottles_of_beer -= 1
12 lines: Classes
class BankAccount(object):
def __init__(self, initial_balance=0):
self.balance = initial_balance
def deposit(self, amount):
self.balance += amount
def withdraw(self, amount):
self.balance -= amount
def overdrawn(self):
return self.balance < 0
my_account = BankAccount(15)
my_account.withdraw(5)
print my_account.balance
13 lines: Unit testing with
unittest
import unittest
def median(pool):
copy = sorted(pool)
size = len(copy)
if size % 2 == 1:
return copy[(size - 1) / 2]
else:
return (copy[size/2 - 1] +
copy[size/2]) / 2
class
TestMedian(unittest.TestCase):
def testMedian(self):
self.failUnlessEqual(median([2, 9, 9,
7, 9, 2, 4, 5, 8]), 7)
if __name__ == '__main__':
unittest.main()
14 lines: Doctest-based
testing
def median(pool):
'''Statistical median to demonstrate doctest.
>>> median([2, 9, 9, 7, 9, 2, 4, 5, 8])
7
'''
copy = sorted(pool)
size = len(copy)
if size % 2 == 1:
return copy[(size - 1) / 2]
else:
return (copy[size/2 - 1] +
copy[size/2]) / 2
if __name__ == '__main__':
import doctest
doctest.testmod()
15 lines: itertools
from itertools import groupby
lines = '''
This is the
first paragraph.
This is the second.
'''.splitlines()
# Use itertools.groupby and bool
to return groups of
# consecutive lines that either
have content or don't.
for has_chars, frags in
groupby(lines, bool):
if has_chars:
print ' '.join(frags)
# PRINTS:
# This is the first paragraph.
# This is the second.
16 lines: csv module, tuple
unpacking, cmp() built-in
import csv
# write stocks data as
comma-separated values
writer =
csv.writer(open('stocks.csv', 'wb', buffering=0))
writer.writerows([
('GOOG', 'Google, Inc.', 505.24, 0.47, 0.09),
('YHOO', 'Yahoo! Inc.', 27.38, 0.33, 1.22),
('CNET', 'CNET Networks, Inc.', 8.62, -0.13, -1.49)
])
# read stocks data, print status
messages
stocks =
csv.reader(open('stocks.csv', 'rb'))
status_labels = {-1: 'down', 0:
'unchanged', 1: 'up'}
for ticker, name, price, change,
pct in stocks:
status = status_labels[cmp(float(change), 0.0)]
print '%s is %s (%s%%)' % (name, status, pct)
18 lines: 8-Queens Problem
(recursion)
BOARD_SIZE = 8
def under_attack(col, queens):
left = right = col
for r, c in reversed(queens):
left, right = left - 1, right + 1
if c in (left, col, right):
return True
return False
def solve(n):
if n == 0:
return [[]]
smaller_solutions = solve(n - 1)
return [solution+[(n,i+1)]
for i in xrange(BOARD_SIZE)
for solution in smaller_solutions
if not under_attack(i+1,
solution)]
for answer in solve(BOARD_SIZE):
print answer
20 lines: Prime numbers
sieve w/fancy generators
import itertools
def iter_primes():
# an iterator of all numbers between 2 and
+infinity
numbers = itertools.count(2)
# generate primes forever
while True:
# get the first number from the
iterator (always a prime)
prime = numbers.next()
yield prime
# this code iteratively builds up a
chain of
# filters...slightly tricky, but
ponder it a bit
numbers =
itertools.ifilter(prime.__rmod__, numbers)
for p in iter_primes():
if p > 1000:
break
print p
21 lines: XML/HTML parsing
(using Python 2.5 or third-party library)
dinner_recipe = '''<html><body><table>
<tr><th>amt</th><th>unit</th><th>item</th></tr>
<tr><td>24</td><td>slices</td><td>baguette</td></tr>
<tr><td>2+</td><td>tbsp</td><td>olive
oil</td></tr>
<tr><td>1</td><td>cup</td><td>tomatoes</td></tr>
<tr><td>1</td><td>jar</td><td>pesto</td></tr>
</table></body></html>'''
# In Python 2.5 or from
http://effbot.org/zone/element-index.htm
import xml.etree.ElementTree as
etree
tree =
etree.fromstring(dinner_recipe)
# For invalid HTML use
http://effbot.org/zone/element-soup.htm
# import ElementSoup, StringIO
# tree =
ElementSoup.parse(StringIO.StringIO(dinner_recipe))
pantry = set(['olive oil',
'pesto'])
for ingredient in
tree.getiterator('tr'):
amt, unit, item = ingredient
if item.tag == "td" and item.text not in pantry:
print "%s: %s %s" %
(item.text, amt.text, unit.text)
28 lines: 8-Queens Problem
(define your own exceptions)
BOARD_SIZE = 8
class BailOut(Exception):
pass
def validate(queens):
left = right = col = queens[-1]
for r in reversed(queens[:-1]):
left, right = left-1, right+1
if r in (left, col, right):
raise BailOut
def add_queen(queens):
for i in range(BOARD_SIZE):
test_queens = queens + [i]
try:
validate(test_queens)
if len(test_queens) == BOARD_SIZE:
return test_queens
else:
return add_queen(test_queens)
except BailOut:
pass
raise BailOut
queens = add_queen([])
print queens
print "\n".join(".
"*q + "Q " + ". "*(BOARD_SIZE-q-1) for q in queens)
import random
guesses_made = 0
name = raw_input('Hello! What is
your name?\n')
number = random.randint(1, 20)
print 'Well, {0}, I am thinking of
a number between 1 and 20.'.format(name)
while guesses_made < 6:
guess = int(raw_input('Take a guess: '))
guesses_made += 1
if guess < number:
print 'Your guess is too low.'
if guess > number:
print 'Your guess is too high.'
if guess == number:
break
if guess == number:
print 'Good job, {0}! You guessed my number in {1}
guesses!'.format(name, guesses_made)
else:
print 'Nope. The number I was thinking of was {0}'.format(number)
