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------ 1 | ------ 1 Output |
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------ 2 | ------ 2 Looping |
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------ 3 | ------ 3 Input, comments |
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------ 4 | ------ 4 Fibonacci, tuple assignment |
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------ 5 | ------ 5 Methods |
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------ 6 | ------ 6 Import, regular expresssions |
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------ 7 | ------ 7 Dictionaries, list comprehensions |
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------ 8 | ------ 8 Command line arguments, exception handling |
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------ 9 | ------ 9 Opening files |
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------ 10 | ------ 10 Time, conditionals |
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------ 11 | ------ 11 Triple-quoted strings, while loop |
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------ 12 | ------ 12 List slicing |
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------ 13 | ------ 13 Unit testing |
These Python examples follow the convention that each program gets one line longer than the one before it. Please try to maintain this convention. I also try to introduce at least one new feature in each program. Also, please see note at the bottom.
------ 1 Output print 'hello world' ------ 2 Looping for name in ('peter', 'paul', 'mary'): print name ------ 3 Input, comments # This is a Python comment. \n is a newline name = raw_input('What is your name?\n') print 'Hi', name ------ 4 Fibonacci, tuple assignment 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) ------ 5 Methods # 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) ------ 6 Import, regular expresssions 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' ------ 7 Dictionaries, list comprehensions 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 Command line arguments, exception handling #!/usr/local/bin/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: print 'Please supply integer arguments' ------ 9 Opening files # 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 ------ 10 Time, conditionals 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 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 List slicing def sieve_of_eratosthenes(candidates): i = 0 while True: divisor = candidates[i] if divisor * divisor > candidates[-1]: return candidates else: i += 1 candidates = candidates[:i] + \ [num for num in candidates[i:] if num % divisor != 0] print sieve_of_eratosthenes(range(2,100)) ------ 13 Unit testing # Let's write reusable code, and unit test it. def add_money_correctly(amounts): # do arithmetic in pennies so as not to accumulate float errors pennies = sum([round(int(amount * 100)) for amount in amounts]) return float(pennies / 100.0) if __name__ == '__main__': for test_args, result in ( ([0.13, 0.02], 0.15), ([100.01, 99.99], 200), ([0, -13.00, 13.00], 0)): if add_money_correctly(test_args) != result: print 'test failed' break
Hi, my name is Steve Howell, and I started this page in May 2007, and I provided the first 10+ or so examples (which may have changed since then).
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 contact me through 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!