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Comment: Warning note that this is Python 2
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← Revision 155 as of 2019-11-09 23:29:53 ⇥
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Remove Python 2-specific information, leaving a link to previous revision for accessibility
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Deletions are marked like this. | Additions are marked like this. |
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Please note that these examples are written in Python 2, and may need some adjustment to run under Python 3. | The examples below will increase in number of lines of code and difficulty: |
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{{{ print 'Hello, world!' }}} ---- |
{{{ print ('Hello, world!') }}} ---- |
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{{{ name = raw_input('What is your name?\n') print 'Hi, %s.' % name }}} ---- |
{{{ name = input('What is your name?\n') print ('Hi, %s.' % name) }}} ---- |
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print "iteration {iteration} is {name}".format(iteration=i, name=name) }}} ---- |
print ("iteration {iteration} is {name}".format(iteration=i, name=name)) }}} ---- |
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print 'This generation has {0} babies'.format(babies) | print ('This generation has {0} babies'.format(babies)) |
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---- |
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print 'Hello', name | print ('Hello', name) |
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print test_string, 'is a valid US local phone number' | print (test_string, 'is a valid US local phone number') |
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print test_string, 'rejected' }}} ---- |
print (test_string, 'rejected') }}} ---- |
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print 'I owe the grocer $%.2f' % grocery_bill }}} ---- |
print ('I owe the grocer $%.2f' % grocery_bill) }}} ---- |
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{{{ #! /usr/bin/env python # This program adds up integers in the command line |
{{{ # This program adds up integers that have been passed as arguments in the command line |
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print 'sum =', total | print ('sum =', total) |
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print 'Please supply integer arguments' }}} ---- |
print ('Please supply integer arguments') }}} ---- |
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print ' ------' + file_name | print (' ------' + file_name) |
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print ' ' + line.rstrip() }}} ---- |
print (' ' + line.rstrip()) print() }}} ---- |
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print activities[activity_time] | print (activities[activity_time]) |
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print 'Unknown, AFK or sleeping!' }}} ---- |
print ('Unknown, AFK or sleeping!') }}} ---- |
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bottles_of_beer = 99 | bottles_of_beer = 9 |
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print REFRAIN % (bottles_of_beer, bottles_of_beer, bottles_of_beer - 1) |
print (REFRAIN % (bottles_of_beer, bottles_of_beer, bottles_of_beer - 1)) |
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my_account.withdraw(5) print my_account.balance }}} ---- |
my_account.withdraw(50) print (my_account.balance, my_account.overdrawn()) }}} ---- |
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return copy[(size - 1) / 2] | return copy[int((size - 1) / 2)] |
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return (copy[size/2 - 1] + copy[size/2]) / 2 | return (copy[int(size/2 - 1)] + copy[int(size/2)]) / 2 |
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self.failUnlessEqual(median([2, 9, 9, 7, 9, 2, 4, 5, 8]), 7) | self.assertEqual(median([2, 9, 9, 7, 9, 2, 4, 5, 8]), 7) |
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7 | 6 #change to 7 in order to pass the test |
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return copy[(size - 1) / 2] | return copy[int((size - 1) / 2)] |
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return (copy[size/2 - 1] + copy[size/2]) / 2 | return (copy[int(size/2 - 1)] + copy[int(size/2)]) / 2 |
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print ' '.join(frags) | print (' '.join(frags)) |
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---- |
---- |
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# need to define cmp function in Python 3 def cmp(a, b): return (a > b) - (a < b) |
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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) ]) |
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] ]) |
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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) }}} ---- |
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))) }}} ---- |
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for i in xrange(BOARD_SIZE) | for i in range(BOARD_SIZE) |
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print answer }}} ---- |
print (answer) }}} ---- |
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prime = numbers.next() | prime = next(numbers) |
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numbers = itertools.ifilter(prime.__rmod__, numbers) | numbers = filter(prime.__rmod__, numbers) |
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print p }}} ---- 21 lines: XML/HTML parsing (using Python 2.5 or third-party library) |
print (p) }}} ---- 21 lines: XML/HTML parsing |
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# In Python 2.5 or from http://effbot.org/zone/element-index.htm | # From http://effbot.org/zone/element-index.htm |
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print "%s: %s %s" % (item.text, amt.text, unit.text) }}} ---- |
print ("%s: %s %s" % (item.text, amt.text, unit.text)) }}} ---- |
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print queens print "\n".join(". "*q + "Q " + ". "*(BOARD_SIZE-q-1) for q in queens) }}} ---- |
print (queens) print ("\n".join(". "*q + "Q " + ". "*(BOARD_SIZE-q-1) for q in queens)) }}} ---- |
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name = raw_input('Hello! What is your name?\n') | name = input('Hello! What is your name?\n') |
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print 'Well, {0}, I am thinking of a number between 1 and 20.'.format(name) | print ('Well, {0}, I am thinking of a number between 1 and 20.'.format(name)) |
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guess = int(raw_input('Take a guess: ')) | guess = int(input('Take a guess: ')) |
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print 'Your guess is too low.' | print ('Your guess is too low.') |
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print 'Your guess is too high.' | print ('Your guess is too high.') |
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print 'Good job, {0}! You guessed my number in {1} guesses!'.format(name, guesses_made) | print ('Good job, {0}! You guessed my number in {1} guesses!'.format(name, guesses_made)) |
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print 'Nope. The number I was thinking of was {0}'.format(number) }}} ---- [[CategoryDocumentation|CategoryDocumentation]] |
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 [[https://wiki.python.org/moin/SimplePrograms?action=recall&rev=154|previous version of this page]]. ---- CategoryDocumentation |
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 -= 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(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.