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These are 10 small Python programs. Please keep programs ordered by size. Here are some example simple programs. Please feel free to contribute, but see notice at bottom, please.

These examples assume version 2.4 or above of Python.
You should be able to run them simply by copying/pasting the code into a file and running Python. Or by inserting this line (#!/bin/env python) at the beginning of your file (Unix/Linux), making the file executable (chmod u+x filename.py) and running it (./filename.py).

    ------ 1 line: Output
{{{#!python
print 'hello world2'
}}}

    ------ 2 lines: Input, assignment, comments

{{{#!python
name = raw_input('What is your name?\n') # \n is a newline
print 'Hi', name
}}}

    ------ 3 lines: For loop, builtin enumerate function
{{{#!python
my_list = ['john', 'pat', 'gary', 'michael']
for i, name in enumerate(my_list):
    print "iteration %i is %s" % (i, name)
}}}

    ------ 4 lines: Fibonacci, tuple assignment
{{{#!python
parents, babies = (1, 1)
while babies < 100:
    print 'This generation has %d babies' % babies
    parents, babies = (babies, parents + babies)
}}}

    ------ 5 lines: Functions
{{{#!python
def greet(name):
    print 'hello', name
greet('Jack')
greet('Jill')
greet('Bob')
}}}

    ------ 6 lines: Import, regular expressions
{{{#!python
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
{{{#!python
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
{{{#!python
#!/usr/bin/env python
# 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
{{{#!python
# indent your Python code to put into an email
import glob
# glob supports Unix style pathname extensions
python_files = glob.glob('*.py')
for fn in sorted(python_files):
    print ' ------', fn
    for line in open(fn):
        print ' ' + line.rstrip()
    print
}}}

    ------ 10 lines: Time, conditionals
{{{#!python
import time
now = time.localtime()
hour = now.tm_hour
if hour < 8: print 'sleeping'
elif hour < 9: print 'commuting'
elif hour < 17: print 'working'
elif hour < 18: print 'commuting'
elif hour < 20: print 'eating'
elif hour < 22: print 'resting'
else: print 'sleeping'
}}}

    ------ 11 lines: Triple-quoted strings, while loop
{{{#!python
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
{{{#!python
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
{{{#!python
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
{{{#!python
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
{{{#!python
import itertools
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 itertools.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
{{{#!python
import csv

# write stocks data as comma-separated values
writer = csv.writer(open('stocks.csv', 'wb'))
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)
{{{#!python
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
{{{#!python
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)
{{{#!python
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)
{{{#!python
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)

}}}
Line 4: Line 314:
    print 'hello world'

    ------
    for name in ('peter', 'paul', 'mary'):
        print name

    ------
    # This is a Python comment. \n is a newline
    name = raw_input('What is your name?\n')
    print 'Hi', name

    ------
    parent_rabbits, baby_rabbits = (1, 1)
    while baby_rabbits < 100:
        print 'This generation has %d rabbits' % baby_rabbits
        parent_rabbits, baby_rabbits = (baby_rabbits, parent_rabbits + baby_rabbits)


    ------
    # def defines a method in Python
    def tax(item_charge, g = 0.05):
        return item_charge * g
    print '%.2f' % tax(11.35)
    print '%.2f' % tax(40.00, 0.08)


    ------
    import re
    for test_string in [ '555-1212', 'ILL-EGAL']:
        if re.match('\d\d\d-\d\d\d\d$', test_string):
            print test_string, 'is a valid US local phone number'
        else:
            print test_string, 'rejected'

    ------
    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


    ------
    class ShoppingCart:
        def __init__(self): self.items = []
        def buy(self, item): self.items.append(item)
        def boughtItems(self): return self.items
    my_cart = ShoppingCart()
    my_cart.buy('apple')
    my_cart.buy('banana')
    print my_cart.boughtItems()


    ------
    # indent your Python code to put into an email
    import glob
    python_files = glob.glob('*.py')
    python_files.sort()
    for fn in python_files:
        print ' ------'
        for line in open(fn):
            print ' ' + line.rstrip()
        print

    ------
    import time
    now = time.localtime()
    hour = now.tm_hour
    if hour < 8: print 'sleeping'
    elif hour < 9: print 'commuting'
    elif hour < 17: print 'working'
    elif hour < 18: print 'commuting'
    elif hour < 20: print 'eating'
    elif hour < 22: print 'resting'
    else: print 'sleeping'

Hi, I started this page in May 2007, and I provided the first 10+ or so examples (which may have changed since then). -- SteveHowell

All code on this page is open source, of course, with the standard Python license.

Minor cleanups are welcome, but if you want to do major restructuring of this page, please run them by the folks on the Python mailing list, or if you are impatient for a response, please just make your own copy of this page. Thanks, and I hope this code is useful for you!

Some goals for this page:

   1) All examples should be simple.

   2) There should be a gentle progression through Python concepts.

----
CategoryLanguage

Here are some example simple programs. Please feel free to contribute, but see notice at bottom, please.

These examples assume version 2.4 or above of Python. You should be able to run them simply by copying/pasting the code into a file and running Python. Or by inserting this line (#!/bin/env python) at the beginning of your file (Unix/Linux), making the file executable (chmod u+x filename.py) and running it (./filename.py).


1 line: Output

   1 print 'hello world2'

2 lines: Input, assignment, comments

   1 name = raw_input('What is your name?\n') # \n is a newline
   2 print 'Hi', name

3 lines: For loop, builtin enumerate function

   1 my_list = ['john', 'pat', 'gary', 'michael']
   2 for i, name in enumerate(my_list):
   3     print "iteration %i is %s" % (i, name)

4 lines: Fibonacci, tuple assignment

   1 parents, babies = (1, 1)
   2 while babies < 100:
   3     print 'This generation has %d babies' % babies
   4     parents, babies = (babies, parents + babies)

5 lines: Functions

   1 def greet(name):
   2     print 'hello', name
   3 greet('Jack')
   4 greet('Jill')
   5 greet('Bob')

6 lines: Import, regular expressions

   1 import re
   2 for test_string in ['555-1212', 'ILL-EGAL']:
   3     if re.match(r'^\d{3}-\d{4}$', test_string):
   4         print test_string, 'is a valid US local phone number'
   5     else:
   6         print test_string, 'rejected'

7 lines: Dictionaries, generator expressions

   1 prices = {'apple': 0.40, 'banana': 0.50}
   2 my_purchase = {
   3     'apple': 1,
   4     'banana': 6}
   5 grocery_bill = sum(prices[fruit] * my_purchase[fruit]
   6                    for fruit in my_purchase)
   7 print 'I owe the grocer $%.2f' % grocery_bill

8 lines: Command line arguments, exception handling

   1 #!/usr/bin/env python
   2 # This program adds up integers in the command line
   3 import sys
   4 try:
   5     total = sum(int(arg) for arg in sys.argv[1:])
   6     print 'sum =', total
   7 except ValueError:
   8     print 'Please supply integer arguments'

9 lines: Opening files

   1 # indent your Python code to put into an email
   2 import glob
   3 # glob supports Unix style pathname extensions
   4 python_files = glob.glob('*.py')
   5 for fn in sorted(python_files):
   6     print '    ------', fn
   7     for line in open(fn):
   8         print '    ' + line.rstrip()
   9     print

10 lines: Time, conditionals

   1 import time
   2 now = time.localtime()
   3 hour = now.tm_hour
   4 if hour < 8: print 'sleeping'
   5 elif hour < 9: print 'commuting'
   6 elif hour < 17: print 'working'
   7 elif hour < 18: print 'commuting'
   8 elif hour < 20: print 'eating'
   9 elif hour < 22: print 'resting'
  10 else: print 'sleeping'

11 lines: Triple-quoted strings, while loop

   1 REFRAIN = '''
   2 %d bottles of beer on the wall,
   3 %d bottles of beer,
   4 take one down, pass it around,
   5 %d bottles of beer on the wall!
   6 '''
   7 bottles_of_beer = 99
   8 while bottles_of_beer > 1:
   9     print REFRAIN % (bottles_of_beer, bottles_of_beer,
  10         bottles_of_beer - 1)
  11     bottles_of_beer -= 1

12 lines: Classes

   1 class BankAccount(object):
   2     def __init__(self, initial_balance=0):
   3         self.balance = initial_balance
   4     def deposit(self, amount):
   5         self.balance += amount
   6     def withdraw(self, amount):
   7         self.balance -= amount
   8     def overdrawn(self):
   9         return self.balance < 0
  10 my_account = BankAccount(15)
  11 my_account.withdraw(5)
  12 print my_account.balance

13 lines: Unit testing with unittest

   1 import unittest
   2 def median(pool):
   3     copy = sorted(pool)
   4     size = len(copy)
   5     if size % 2 == 1:
   6         return copy[(size - 1) / 2]
   7     else:
   8         return (copy[size/2 - 1] + copy[size/2]) / 2
   9 class TestMedian(unittest.TestCase):
  10     def testMedian(self):
  11         self.failUnlessEqual(median([2, 9, 9, 7, 9, 2, 4, 5, 8]), 7)
  12 if __name__ == '__main__':
  13     unittest.main()

14 lines: Doctest-based testing

   1 def median(pool):
   2     '''Statistical median to demonstrate doctest.
   3     >>> median([2, 9, 9, 7, 9, 2, 4, 5, 8])
   4     7
   5     '''
   6     copy = sorted(pool)
   7     size = len(copy)
   8     if size % 2 == 1:
   9         return copy[(size - 1) / 2]
  10     else:
  11         return (copy[size/2 - 1] + copy[size/2]) / 2
  12 if __name__ == '__main__':
  13     import doctest
  14     doctest.testmod()

15 lines: itertools

   1 import itertools
   2 lines = '''
   3 This is the
   4 first paragraph.
   5 
   6 This is the second.
   7 '''.splitlines()
   8 # Use itertools.groupby and bool to return groups of
   9 # consecutive lines that either have content or don't.
  10 for has_chars, frags in itertools.groupby(lines, bool):
  11     if has_chars:
  12         print ' '.join(frags)
  13 # PRINTS:
  14 # This is the first paragraph.
  15 # This is the second.

16 lines: csv module, tuple unpacking, cmp() built-in

   1 import csv
   2 
   3 # write stocks data as comma-separated values
   4 writer = csv.writer(open('stocks.csv', 'wb'))
   5 writer.writerows([
   6     ('GOOG', 'Google, Inc.', 505.24, 0.47, 0.09),
   7     ('YHOO', 'Yahoo! Inc.', 27.38, 0.33, 1.22),
   8     ('CNET', 'CNET Networks, Inc.', 8.62, -0.13, -1.49)
   9 ])
  10 
  11 # read stocks data, print status messages
  12 stocks = csv.reader(open('stocks.csv', 'rb'))
  13 status_labels = {-1: 'down', 0: 'unchanged', 1: 'up'}
  14 for ticker, name, price, change, pct in stocks:
  15     status = status_labels[cmp(float(change), 0.0)]
  16     print '%s is %s (%s%%)' % (name, status, pct)

18 lines: 8-Queens Problem (recursion)

   1 BOARD_SIZE = 8
   2 
   3 def under_attack(col, queens):
   4     left = right = col
   5     for r, c in reversed(queens):
   6         left, right = left-1, right+1
   7         if c in (left, col, right):
   8             return True
   9     return False
  10 
  11 def solve(n):
  12     if n == 0: return [[]]
  13     smaller_solutions = solve(n-1)
  14     return [solution+[(n,i+1)]
  15         for i in range(BOARD_SIZE)
  16             for solution in smaller_solutions
  17                 if not under_attack(i+1, solution)]
  18 for answer in solve(BOARD_SIZE): print answer

20 lines: Prime numbers sieve w/fancy generators

   1 import itertools
   2 
   3 def iter_primes():
   4      # an iterator of all numbers between 2 and +infinity
   5      numbers = itertools.count(2)
   6 
   7      # generate primes forever
   8      while True:
   9          # get the first number from the iterator (always a prime)
  10          prime = numbers.next()
  11          yield prime
  12 
  13          # this code iteratively builds up a chain of
  14          # filters...slightly tricky, but ponder it a bit
  15          numbers = itertools.ifilter(prime.__rmod__, numbers)
  16 
  17 for p in iter_primes():
  18     if p > 1000:
  19         break
  20     print p

21 lines: XML/HTML parsing (using Python 2.5 or third-party library)

   1 dinner_recipe = '''<html><body><table>
   2 <tr><th>amt</th><th>unit</th><th>item</th></tr>
   3 <tr><td>24</td><td>slices</td><td>baguette</td></tr>
   4 <tr><td>2+</td><td>tbsp</td><td>olive oil</td></tr>
   5 <tr><td>1</td><td>cup</td><td>tomatoes</td></tr>
   6 <tr><td>1</td><td>jar</td><td>pesto</td></tr>
   7 </table></body></html>'''
   8 
   9 # In Python 2.5 or from http://effbot.org/zone/element-index.htm
  10 import xml.etree.ElementTree as etree
  11 tree = etree.fromstring(dinner_recipe)
  12 
  13 # For invalid HTML use http://effbot.org/zone/element-soup.htm
  14 # import ElementSoup, StringIO
  15 # tree = ElementSoup.parse(StringIO.StringIO(dinner_recipe))
  16 
  17 pantry = set(['olive oil', 'pesto'])
  18 for ingredient in tree.getiterator('tr'):
  19     amt, unit, item = ingredient
  20     if item.tag == "td" and item.text not in pantry:
  21         print "%s: %s %s" % (item.text, amt.text, unit.text)

28 lines: 8-Queens Problem (define your own exceptions)

   1 BOARD_SIZE = 8
   2 
   3 class BailOut(Exception):
   4     pass
   5 
   6 def validate(queens):
   7     left = right = col = queens[-1]
   8     for r in reversed(queens[:-1]):
   9         left, right = left-1, right+1
  10         if r in (left, col, right):
  11             raise BailOut
  12 
  13 def add_queen(queens):
  14     for i in range(BOARD_SIZE):
  15         test_queens = queens + [i]
  16         try:
  17             validate(test_queens)
  18             if len(test_queens) == BOARD_SIZE:
  19                 return test_queens
  20             else:
  21                 return add_queen(test_queens)
  22         except BailOut:
  23             pass
  24     raise BailOut
  25 
  26 queens = add_queen([])
  27 print queens
  28 print "\n".join(". "*q + "Q " + ". "*(BOARD_SIZE-q-1) for q in queens)

Hi, I started this page in May 2007, and I provided the first 10+ or so examples (which may have changed since then). -- SteveHowell

All code on this page is open source, of course, with the standard Python license.

Minor cleanups are welcome, but if you want to do major restructuring of this page, please run them by the folks on the Python mailing list, or if you are impatient for a response, please just make your own copy of this page. Thanks, and I hope this code is useful for you!

Some goals for this page:

  • 1) All examples should be simple. 2) There should be a gentle progression through Python concepts.


CategoryLanguage

SimplePrograms (last edited 2015-06-13 04:34:34 by SteveHolden)

Unable to edit the page? See the FrontPage for instructions.