9512
Comment: revert spam
|
10759
Changing code to Python 3 syntax
|
Deletions are marked like this. | Additions are marked like this. |
Line 1: | Line 1: |
Please note that these examples were changed to run under Python 3. The Python2orPython3 page provides advice on how to decide which one will best suit your needs. Some differences from Python 2 to Python 3: {{{ # Python 2 syntax print 'Hello, world!' raw_input('What is your name?\n') self.failUnlessEqual(median([2, 9, 9, 7, 9, 2, 4, 5, 8]), 7) # Unit testing with unittest copy[(size - 1) / 2] # access of a list index without casting to int xrange(BOARD_SIZE) # xrange exists cmp(1.0, 0.0) # cmp function exists iteratable.next() # list iteration itertools.ifilter(prime.__rmod__, iteratable) # itertools.ifilter is filter in Python 3 # Python 3 syntax print('Hello, World!') input('What is your name?\n') self.assertEqual(median([2, 9, 9, 7, 9, 2, 4, 5, 8]), 7) # Unit testing with unittest, failUnlessEqual deprecated copy[int((size - 1) / 2)] # access of a list index needs casting to int range(BOARD_SIZE) # xrange was renamed to range in Python 3 #cmp needs to be implemented! def cmp(a, b): return (a > b) - (a < b) next(iteratable) # list iteration filter(prime.__rmod__, iteratable) # is itertools.ifilter in Python 2 }}} The examples below will increase in number of lines of code and difficulty: |
|
Line 3: | Line 32: |
{{{ print 'Hello, world!' }}} ---- |
{{{ print ('Hello, world!') }}} ---- |
Line 19: | Line 38: |
{{{ name = raw_input('What is your name?\n') print 'Hi, %s.' % name }}} ---- |
{{{ name = input('What is your name?\n') print ('Hi, %s.' % name) }}} ---- |
Line 35: | Line 44: |
Line 45: | Line 48: |
print "iteration {iteration} is {name}".format(iteration=i, name=name) }}} ---- |
print ("iteration {iteration} is {name}".format(iteration=i, name=name)) }}} ---- |
Line 53: | Line 52: |
Line 63: | Line 56: |
print 'This generation has {0} babies'.format(babies) | print ('This generation has {0} babies'.format(babies)) |
Line 66: | Line 59: |
---- |
---- |
Line 73: | Line 62: |
Line 81: | Line 64: |
print 'Hello', name | print ('Hello', name) |
Line 86: | Line 70: |
---- |
---- |
Line 92: | Line 72: |
Line 103: | Line 77: |
print test_string, 'is a valid US local phone number' | print (test_string, 'is a valid US local phone number') |
Line 105: | Line 79: |
print test_string, 'rejected' }}} ---- |
print (test_string, 'rejected') }}} ---- |
Line 113: | Line 83: |
Line 127: | Line 91: |
print 'I owe the grocer $%.2f' % grocery_bill }}} ---- |
print ('I owe the grocer $%.2f' % grocery_bill) }}} ---- |
Line 136: | Line 96: |
{{{ #! /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 |
Line 149: | Line 101: |
print 'sum =', total | print ('sum =', total) |
Line 151: | Line 103: |
print 'Please supply integer arguments' }}} ---- |
print ('Please supply integer arguments') }}} ---- |
Line 159: | Line 107: |
Line 172: | Line 114: |
print ' ------' + file_name | print (' ------' + file_name) |
Line 176: | Line 118: |
print ' ' + line.rstrip() }}} ---- |
print (' ' + line.rstrip()) print() }}} ---- |
Line 186: | Line 124: |
Line 208: | Line 140: |
print activities[activity_time] | print (activities[activity_time]) |
Line 211: | Line 143: |
print 'Unknown, AFK or sleeping!' }}} ---- |
print ('Unknown, AFK or sleeping!') }}} ---- |
Line 219: | Line 147: |
Line 233: | Line 155: |
bottles_of_beer = 99 | bottles_of_beer = 9 |
Line 235: | Line 157: |
print REFRAIN % (bottles_of_beer, bottles_of_beer, bottles_of_beer - 1) |
print (REFRAIN % (bottles_of_beer, bottles_of_beer, bottles_of_beer - 1)) |
Line 239: | Line 161: |
---- |
---- |
Line 245: | Line 163: |
Line 263: | Line 175: |
my_account.withdraw(5) print my_account.balance }}} ---- |
my_account.withdraw(50) print (my_account.balance, my_account.overdrawn()) }}} ---- |
Line 272: | Line 180: |
Line 285: | Line 187: |
return copy[(size - 1) / 2] | return copy[int((size - 1) / 2)] |
Line 287: | Line 189: |
return (copy[size/2 - 1] + copy[size/2]) / 2 | return (copy[int(size/2 - 1)] + copy[int(size/2)]) / 2 |
Line 290: | Line 192: |
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) |
Line 294: | Line 196: |
---- |
---- |
Line 300: | Line 198: |
Line 311: | Line 203: |
7 | 6 #change to 7 in order to pass the test |
Line 316: | Line 208: |
return copy[(size - 1) / 2] | return copy[int((size - 1) / 2)] |
Line 318: | Line 210: |
return (copy[size/2 - 1] + copy[size/2]) / 2 | return (copy[int(size/2 - 1)] + copy[int(size/2)]) / 2 |
Line 323: | Line 215: |
---- |
---- |
Line 329: | Line 217: |
Line 348: | Line 230: |
print ' '.join(frags) | print (' '.join(frags)) |
Line 353: | Line 235: |
---- |
---- |
Line 360: | Line 238: |
Line 369: | Line 241: |
# need to define cmp function in Python 3 def cmp(a, b): return (a > b) - (a < b) |
|
Line 370: | Line 246: |
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] ]) |
Line 378: | Line 255: |
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))) }}} ---- |
Line 390: | Line 265: |
Line 417: | Line 286: |
for i in xrange(BOARD_SIZE) | for i in range(BOARD_SIZE) |
Line 421: | Line 290: |
print answer }}} ---- |
print (answer) }}} ---- |
Line 429: | Line 294: |
Line 446: | Line 305: |
prime = numbers.next() | prime = next(numbers) |
Line 451: | Line 310: |
numbers = itertools.ifilter(prime.__rmod__, numbers) | numbers = filter(prime.__rmod__, numbers) |
Line 456: | Line 315: |
print p }}} ---- 21 lines: XML/HTML parsing (using Python 2.5 or third-party library) |
print (p) }}} ---- 21 lines: XML/HTML parsing (using Python 2.5 or third-party library) (this example is in Python 2 syntax) |
Line 494: | Line 343: |
---- 28 lines: 8-Queens Problem (define your own exceptions) |
---- 28 lines (this example is in Python 2 syntax): 8-Queens Problem (define your own exceptions) |
Line 537: | Line 376: |
---- 33 lines: "Guess the Number" Game (edited) from http://inventwithpython.com |
---- 33 lines (this example is in Python 2 syntax): "Guess the Number" Game (edited) from http://inventwithpython.com |
Line 580: | Line 409: |
---- [[CategoryDocumentation|CategoryDocumentation]] |
---- CategoryDocumentation |
Please note that these examples were changed to run under Python 3. The Python2orPython3 page provides advice on how to decide which one will best suit your needs.
Some differences from Python 2 to Python 3:
# Python 2 syntax print 'Hello, world!' raw_input('What is your name?\n') self.failUnlessEqual(median([2, 9, 9, 7, 9, 2, 4, 5, 8]), 7) # Unit testing with unittest copy[(size - 1) / 2] # access of a list index without casting to int xrange(BOARD_SIZE) # xrange exists cmp(1.0, 0.0) # cmp function exists iteratable.next() # list iteration itertools.ifilter(prime.__rmod__, iteratable) # itertools.ifilter is filter in Python 3 # Python 3 syntax print('Hello, World!') input('What is your name?\n') self.assertEqual(median([2, 9, 9, 7, 9, 2, 4, 5, 8]), 7) # Unit testing with unittest, failUnlessEqual deprecated copy[int((size - 1) / 2)] # access of a list index needs casting to int range(BOARD_SIZE) # xrange was renamed to range in Python 3 #cmp needs to be implemented! def cmp(a, b): return (a > b) - (a < b) next(iteratable) # list iteration filter(prime.__rmod__, iteratable) # is itertools.ifilter in Python 2
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 (using Python 2.5 or third-party library) (this example is in Python 2 syntax)
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 (this example is in Python 2 syntax): 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 (this example is in Python 2 syntax): "Guess the Number" Game (edited) from http://inventwithpython.com
import random guesses_made = 0 name = 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 += 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)