Please note that these examples are written in Python 2, and may need some adjustment to run under Python 3.

1 line: Output

print 'Hello, world!'

2 lines: Input, assignment

name = raw_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 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_namewith open(file_name) as f:for line in f:print '    ' + line.rstrip()print

10 lines: Time, conditionals, from..import, for..else

from time import localtimeactivities = {8: 'Sleeping',9: 'Commuting',17: 'Working',18: 'Commuting',20: 'Eating',22: 'Resting' }time_now = localtime()
hour = time_now.tm_hourfor 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 = 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_balancedef deposit(self, amount):self.balance += amountdef withdraw(self, amount):self.balance -= amountdef 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 doctestdoctest.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 = 8def under_attack(col, queens):left = right = colfor r, c in reversed(queens):left, right = left - 1, right + 1if c in (left, col, right):return Truereturn Falsedef 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_solutionsif not under_attack(i+1, solution)]
for answer in solve(BOARD_SIZE):print answer

20 lines: Prime numbers sieve w/fancy generators

import itertoolsdef iter_primes():# an iterator of all numbers between 2 and +infinitynumbers = itertools.count(2)# generate primes foreverwhile 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 bitnumbers = itertools.ifilter(prime.__rmod__, numbers)for p in iter_primes():if p > 1000:breakprint 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 = ingredientif 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 = 8class BailOut(Exception):passdef validate(queens):left = right = col = queens[-1]for r in reversed(queens[:-1]):left, right = left-1, right+1if r in (left, col, right):raise BailOutdef 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_queenselse:return add_queen(test_queens)except BailOut:passraise BailOutqueens = 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 randomguesses_made = 0name = 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 += 1if guess < number:print 'Your guess is too low.'if guess > number:print 'Your guess is too high.'if guess == number:breakif 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)