The examples below will increase in number of lines of code and difficulty:
1 line: Output
print ('Hello, world!')2 lines: Input, assignment
name = input('What is your name?\n')
print ('Hi, %s.' % name)3 lines: For loop, built-in enumerate function, new style formatting
friends = ['john', 'pat', 'gary', 'michael']
for i, name in enumerate(friends):
print ("iteration {iteration} is {name}".format(iteration=i, name=name))4 lines: Fibonacci, tuple assignment
parents, babies = (1, 1)
while babies < 100:
print ('This generation has {0} babies'.format(babies))
parents, babies = (babies, parents + babies)5 lines: Functions
def greet(name):
print ('Hello', name)
greet('Jack')
greet('Jill')
greet('Bob')6 lines: Import, regular expressions
import re
for test_string in ['555-1212', 'ILL-EGAL']:
if re.match(r'^\d{3}-\d{4}$', test_string):
print (test_string, 'is a valid US local phone number')
else:
print (test_string, 'rejected')7 lines: Dictionaries, generator expressions
prices = {'apple': 0.40, 'banana': 0.50}
my_purchase = {
'apple': 1,
'banana': 6}
grocery_bill = sum(prices[fruit] * my_purchase[fruit]
for fruit in my_purchase)
print ('I owe the grocer $%.2f' % grocery_bill)8 lines: Command line arguments, exception handling
# This program adds up integers that have been passed as arguments in the command line
import sys
try:
total = sum(int(arg) for arg in sys.argv[1:])
print ('sum =', total)
except ValueError:
print ('Please supply integer arguments')9 lines: Opening files
# indent your Python code to put into an email
import glob
# glob supports Unix style pathname extensions
python_files = glob.glob('*.py')
for file_name in sorted(python_files):
print (' ------' + file_name)
with open(file_name) as f:
for line in f:
print (' ' + line.rstrip())
print()10 lines: Time, conditionals, from..import, for..else
from time import localtime
activities = {8: 'Sleeping',
9: 'Commuting',
17: 'Working',
18: 'Commuting',
20: 'Eating',
22: 'Resting' }
time_now = localtime()
hour = time_now.tm_hour
for activity_time in sorted(activities.keys()):
if hour < activity_time:
print (activities[activity_time])
break
else:
print ('Unknown, AFK or sleeping!')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 = 9
while bottles_of_beer > 1:
print (REFRAIN % (bottles_of_beer, bottles_of_beer,
bottles_of_beer - 1))
bottles_of_beer -= 112 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(50)
print (my_account.balance, my_account.overdrawn())13 lines: Unit testing with unittest
import unittest
def median(pool):
copy = sorted(pool)
size = len(copy)
if size % 2 == 1:
return copy[int((size - 1) / 2)]
else:
return (copy[int(size/2 - 1)] + copy[int(size/2)]) / 2
class TestMedian(unittest.TestCase):
def testMedian(self):
self.assertEqual(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])
6 #change to 7 in order to pass the test
'''
copy = sorted(pool)
size = len(copy)
if size % 2 == 1:
return copy[int((size - 1) / 2)]
else:
return (copy[int(size/2 - 1)] + copy[int(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
# need to define cmp function in Python 3
def cmp(a, b):
return (a > b) - (a < b)
# write stocks data as comma-separated values
with open('stocks.csv', 'w', newline='') as stocksFileW:
writer = csv.writer(stocksFileW)
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, -1.4901]
])
# read stocks data, print status messages
with open('stocks.csv', 'r') as stocksFile:
stocks = csv.reader(stocksFile)
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 (%.2f)' % (name, status, float(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 range(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 = next(numbers)
yield prime
# this code iteratively builds up a chain of
# filters...slightly tricky, but ponder it a bit
numbers = filter(prime.__rmod__, numbers)
for p in iter_primes():
if p > 1000:
break
print (p)21 lines: XML/HTML parsing
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>'''
# 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))33 lines: "Guess the Number" Game (edited) from http://inventwithpython.com
import random
guesses_made = 0
name = 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(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))These all run under Python 3. If you are interested in differences between Python 2 and Python 3, please take a look at the previous version of this page.