Curso de Python

KMEE <suporte@kmee.com.br>

Prefácio

“Python é uma linguagem de programação poderosa e fácil de aprender” Python Tutorial oficial.

  • Curso para pessoas com pouca experiência em programação que querem aprender Python;
  • É voltado para pessoas que têm um pouco de experiência em qualquer linguagem de programação, o suficiente para saber o que é uma variável ou “if”.
  • +- 2 dias de python básico;

“Um desenvolvedor experiente pode começar a escrever um programa Python útil em questões de horas. À medida que as primeiras horas produtivas se transformam em semanas e meses, muitos programadores continuam escrevendo código python com um sotaque bem marcado.”. :) Luciano Ramalho

  • Só sentimos falta daquilo que conhecemos ...
  • “Pythonico”

Python Data Model

Contatos

Exercícios

Exercício 1 - list1.py

Download do Arquivo: list1.py

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#!/usr/bin/python -tt
# Copyright 2010 Google Inc.
# Licensed under the Apache License, Version 2.0
# http://www.apache.org/licenses/LICENSE-2.0

# Google's Python Class
# http://code.google.com/edu/languages/google-python-class/

# Basic list exercises
# Fill in the code for the functions below. main() is already set up
# to call the functions with a few different inputs,
# printing 'OK' when each function is correct.
# The starter code for each function includes a 'return'
# which is just a placeholder for your code.
# It's ok if you do not complete all the functions, and there
# are some additional functions to try in list2.py.

# A. match_ends
# Given a list of strings, return the count of the number of
# strings where the string length is 2 or more and the first
# and last chars of the string are the same.
# Note: python does not have a ++ operator, but += works.
def match_ends(words):
  # +++your code here+++
  return


# B. front_x
# Given a list of strings, return a list with the strings
# in sorted order, except group all the strings that begin with 'x' first.
# e.g. ['mix', 'xyz', 'apple', 'xanadu', 'aardvark'] yields
# ['xanadu', 'xyz', 'aardvark', 'apple', 'mix']
# Hint: this can be done by making 2 lists and sorting each of them
# before combining them.
def front_x(words):
  # +++your code here+++
  return



# C. sort_last
# Given a list of non-empty tuples, return a list sorted in increasing
# order by the last element in each tuple.
# e.g. [(1, 7), (1, 3), (3, 4, 5), (2, 2)] yields
# [(2, 2), (1, 3), (3, 4, 5), (1, 7)]
# Hint: use a custom key= function to extract the last element form each tuple.
def sort_last(tuples):
  # +++your code here+++
  return


# Simple provided test() function used in main() to print
# what each function returns vs. what it's supposed to return.
def test(got, expected):
  if got == expected:
    prefix = ' OK '
  else:
    prefix = '  X '
  print '%s got: %s expected: %s' % (prefix, repr(got), repr(expected))


# Calls the above functions with interesting inputs.
def main():
  print 'match_ends'
  test(match_ends(['aba', 'xyz', 'aa', 'x', 'bbb']), 3)
  test(match_ends(['', 'x', 'xy', 'xyx', 'xx']), 2)
  test(match_ends(['aaa', 'be', 'abc', 'hello']), 1)

  print
  print 'front_x'
  test(front_x(['bbb', 'ccc', 'axx', 'xzz', 'xaa']),
       ['xaa', 'xzz', 'axx', 'bbb', 'ccc'])
  test(front_x(['ccc', 'bbb', 'aaa', 'xcc', 'xaa']),
       ['xaa', 'xcc', 'aaa', 'bbb', 'ccc'])
  test(front_x(['mix', 'xyz', 'apple', 'xanadu', 'aardvark']),
       ['xanadu', 'xyz', 'aardvark', 'apple', 'mix'])

       
  print
  print 'sort_last'
  test(sort_last([(1, 3), (3, 2), (2, 1)]),
       [(2, 1), (3, 2), (1, 3)])
  test(sort_last([(2, 3), (1, 2), (3, 1)]),
       [(3, 1), (1, 2), (2, 3)])
  test(sort_last([(1, 7), (1, 3), (3, 4, 5), (2, 2)]),
       [(2, 2), (1, 3), (3, 4, 5), (1, 7)])


if __name__ == '__main__':
  main()

Exercício 2 - list2.py

Download do Arquivo: list2.py

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#!/usr/bin/python -tt
# Copyright 2010 Google Inc.
# Licensed under the Apache License, Version 2.0
# http://www.apache.org/licenses/LICENSE-2.0

# Google's Python Class
# http://code.google.com/edu/languages/google-python-class/

# Additional basic list exercises

# D. Given a list of numbers, return a list where
# all adjacent == elements have been reduced to a single element,
# so [1, 2, 2, 3] returns [1, 2, 3]. You may create a new list or
# modify the passed in list.
def remove_adjacent(nums):
  # +++your code here+++
  return


# E. Given two lists sorted in increasing order, create and return a merged
# list of all the elements in sorted order. You may modify the passed in lists.
# Ideally, the solution should work in "linear" time, making a single
# pass of both lists.
def linear_merge(list1, list2):
  # +++your code here+++
  return

# Note: the solution above is kind of cute, but unforunately list.pop(0)
# is not constant time with the standard python list implementation, so
# the above is not strictly linear time.
# An alternate approach uses pop(-1) to remove the endmost elements
# from each list, building a solution list which is backwards.
# Then use reversed() to put the result back in the correct order. That
# solution works in linear time, but is more ugly.


# Simple provided test() function used in main() to print
# what each function returns vs. what it's supposed to return.
def test(got, expected):
  if got == expected:
    prefix = ' OK '
  else:
    prefix = '  X '
  print '%s got: %s expected: %s' % (prefix, repr(got), repr(expected))


# Calls the above functions with interesting inputs.
def main():
  print 'remove_adjacent'
  test(remove_adjacent([1, 2, 2, 3]), [1, 2, 3])
  test(remove_adjacent([2, 2, 3, 3, 3]), [2, 3])
  test(remove_adjacent([]), [])

  print
  print 'linear_merge'
  test(linear_merge(['aa', 'xx', 'zz'], ['bb', 'cc']),
       ['aa', 'bb', 'cc', 'xx', 'zz'])
  test(linear_merge(['aa', 'xx'], ['bb', 'cc', 'zz']),
       ['aa', 'bb', 'cc', 'xx', 'zz'])
  test(linear_merge(['aa', 'aa'], ['aa', 'bb', 'bb']),
       ['aa', 'aa', 'aa', 'bb', 'bb'])


if __name__ == '__main__':
  main()

Exercício 3 - string1.py

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#!/usr/bin/python -tt
# Copyright 2010 Google Inc.
# Licensed under the Apache License, Version 2.0
# http://www.apache.org/licenses/LICENSE-2.0

# Google's Python Class
# http://code.google.com/edu/languages/google-python-class/

# Basic string exercises
# Fill in the code for the functions below. main() is already set up
# to call the functions with a few different inputs,
# printing 'OK' when each function is correct.
# The starter code for each function includes a 'return'
# which is just a placeholder for your code.
# It's ok if you do not complete all the functions, and there
# are some additional functions to try in string2.py.


# A. donuts
# Given an int count of a number of donuts, return a string
# of the form 'Number of donuts: <count>', where <count> is the number
# passed in. However, if the count is 10 or more, then use the word 'many'
# instead of the actual count.
# So donuts(5) returns 'Number of donuts: 5'
# and donuts(23) returns 'Number of donuts: many'
def donuts(count):



  return 'Number of donuts: ' + str(count)


# B. both_ends
# Given a string s, return a string made of the first 2
# and the last 2 chars of the original string,
# so 'spring' yields 'spng'. However, if the string length
# is less than 2, return instead the empty string.
def both_ends(s):
  # +++your code here+++
  return


# C. fix_start
# Given a string s, return a string
# where all occurences of its first char have
# been changed to '*', except do not change
# the first char itself.
# e.g. 'babble' yields 'ba**le'
# Assume that the string is length 1 or more.
# Hint: s.replace(stra, strb) returns a version of string s
# where all instances of stra have been replaced by strb.
def fix_start(s):
  # +++your code here+++
  return


# D. MixUp
# Given strings a and b, return a single string with a and b separated
# by a space '<a> <b>', except swap the first 2 chars of each string.
# e.g.
#   'mix', 'pod' -> 'pox mid'
#   'dog', 'dinner' -> 'dig donner'
# Assume a and b are length 2 or more.
def mix_up(a, b):
  # +++your code here+++
  return


# Provided simple test() function used in main() to print
# what each function returns vs. what it's supposed to return.
def test(got, expected):
  if got == expected:
    prefix = ' OK '
  else:
    prefix = '  X '
  print '%s got: %s expected: %s' % (prefix, repr(got), repr(expected))


# Provided main() calls the above functions with interesting inputs,
# using test() to check if each result is correct or not.
def main():
  print 'donuts'
  # Each line calls donuts, compares its result to the expected for that call.
  test(donuts(4), 'Number of donuts: 4')
  test(donuts(9), 'Number of donuts: 9')
  test(donuts(10), 'Number of donuts: many')
  test(donuts(99), 'Number of donuts: many')

  print
  print 'both_ends'
  test(both_ends('spring'), 'spng')
  test(both_ends('Hello'), 'Helo')
  test(both_ends('a'), '')
  test(both_ends('xyz'), 'xyyz')

  
  print
  print 'fix_start'
  test(fix_start('babble'), 'ba**le')
  test(fix_start('aardvark'), 'a*rdv*rk')
  test(fix_start('google'), 'goo*le')
  test(fix_start('donut'), 'donut')

  print
  print 'mix_up'
  test(mix_up('mix', 'pod'), 'pox mid')
  # test(mix_up('Felipe', 'Eder'), 'Edlipe Feer')
  test(mix_up('dog', 'dinner'), 'dig donner')
  test(mix_up('gnash', 'sport'), 'spash gnort')
  test(mix_up('pezzy', 'firm'), 'fizzy perm')


# Standard boilerplate to call the main() function.
if __name__ == '__main__':
  main()

Exercício 4 - string2.py

Download do Arquivo: string2.py

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#!/usr/bin/python2.4 -tt
# Copyright 2010 Google Inc.
# Licensed under the Apache License, Version 2.0
# http://www.apache.org/licenses/LICENSE-2.0

# Google's Python Class
# http://code.google.com/edu/languages/google-python-class/

# Additional basic string exercises

# D. verbing
# Given a string, if its length is at least 3,
# add 'ing' to its end.
# Unless it already ends in 'ing', in which case
# add 'ly' instead.
# If the string length is less than 3, leave it unchanged.
# Return the resulting string.
def verbing(s):
  # +++your code here+++
  return


# E. not_bad
# Given a string, find the first appearance of the
# substring 'not' and 'bad'. If the 'bad' follows
# the 'not', replace the whole 'not'...'bad' substring
# with 'good'.
# Return the resulting string.
# So 'This dinner is not that bad!' yields:
# This dinner is good!
def not_bad(s):
  # +++your code here+++
  return


# F. front_back
# Consider dividing a string into two halves.
# If the length is even, the front and back halves are the same length.
# If the length is odd, we'll say that the extra char goes in the front half.
# e.g. 'abcde', the front half is 'abc', the back half 'de'.
# Given 2 strings, a and b, return a string of the form
#  a-front + b-front + a-back + b-back
def front_back(a, b):
  # +++your code here+++
  return


# Simple provided test() function used in main() to print
# what each function returns vs. what it's supposed to return.
def test(got, expected):
  if got == expected:
    prefix = ' OK '
  else:
    prefix = '  X '
  print '%s got: %s expected: %s' % (prefix, repr(got), repr(expected))


# main() calls the above functions with interesting inputs,
# using the above test() to check if the result is correct or not.
def main():
  print 'verbing'
  test(verbing('hail'), 'hailing')
  test(verbing('swiming'), 'swimingly')
  test(verbing('do'), 'do')

  print
  print 'not_bad'
  test(not_bad('This movie is not so bad'), 'This movie is good')
  test(not_bad('This dinner is not that bad!'), 'This dinner is good!')
  test(not_bad('This tea is not hot'), 'This tea is not hot')
  test(not_bad("It's bad yet not"), "It's bad yet not")

  print
  print 'front_back'
  test(front_back('abcd', 'xy'), 'abxcdy')
  test(front_back('abcde', 'xyz'), 'abcxydez')
  test(front_back('Kitten', 'Donut'), 'KitDontenut')

if __name__ == '__main__':
  main()

Exercicio 5 - wordcount.py

Download do Arquivo: wordcount.py

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#!/usr/bin/python -tt
# Copyright 2010 Google Inc.
# Licensed under the Apache License, Version 2.0
# http://www.apache.org/licenses/LICENSE-2.0

# Google's Python Class
# http://code.google.com/edu/languages/google-python-class/

"""Wordcount exercise
Google's Python class

The main() below is already defined and complete. It calls print_words()
and print_top() functions which you write.

1. For the --count flag, implement a print_words(filename) function that counts
how often each word appears in the text and prints:
word1 count1
word2 count2
...

Print the above list in order sorted by word (python will sort punctuation to
come before letters -- that's fine). Store all the words as lowercase,
so 'The' and 'the' count as the same word.

2. For the --topcount flag, implement a print_top(filename) which is similar
to print_words() but which prints just the top 20 most common words sorted
so the most common word is first, then the next most common, and so on.

Use str.split() (no arguments) to split on all whitespace.

Workflow: don't build the whole program at once. Get it to an intermediate
milestone and print your data structure and sys.exit(0).
When that's working, try for the next milestone.

Optional: define a helper function to avoid code duplication inside
print_words() and print_top().

"""

import sys

# +++your code here+++
# Define print_words(filename) and print_top(filename) functions.
# You could write a helper utility function that reads a file
# and builds and returns a word/count dict for it.
# Then print_words() and print_top() can just call the utility function.

###

# This basic command line argument parsing code is provided and
# calls the print_words() and print_top() functions which you must define.
def main():
  if len(sys.argv) != 3:
    print 'usage: ./wordcount.py {--count | --topcount} file'
    sys.exit(1)

  option = sys.argv[1]
  filename = sys.argv[2]
  if option == '--count':
    print_words(filename)
  elif option == '--topcount':
    print_top(filename)
  else:
    print 'unknown option: ' + option
    sys.exit(1)

if __name__ == '__main__':
  main()

Exercício 6 - logpuzzle.py

Download do Arquivo: logpuzzle.py

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#!/usr/bin/python
# Copyright 2010 Google Inc.
# Licensed under the Apache License, Version 2.0
# http://www.apache.org/licenses/LICENSE-2.0

# Google's Python Class
# http://code.google.com/edu/languages/google-python-class/

import os
import re
import sys
import urllib

"""Logpuzzle exercise
Given an apache logfile, find the puzzle urls and download the images.

Here's what a puzzle url looks like:
10.254.254.28 - - [06/Aug/2007:00:13:48 -0700] "GET /~foo/puzzle-bar-aaab.jpg HTTP/1.0" 302 528 "-" "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.6) Gecko/20070725 Firefox/2.0.0.6"
"""


def read_urls(filename):
  """Returns a list of the puzzle urls from the given log file,
  extracting the hostname from the filename itself.
  Screens out duplicate urls and returns the urls sorted into
  increasing order by its last 4 digits before '.jpg' ."""
  # +++your code here+++
  

def download_images(img_urls, dest_dir):
  """Given the urls already in the correct order, downloads
  each image into the given directory.
  Gives the images local filenames img0, img1, and so on.
  Creates an index.html in the directory
  with an img tag to show each local image file.
  Creates the directory if necessary.
  """
  # +++your code here+++
  

def main():
  args = sys.argv[1:]

  if not args:
    print 'usage: [--todir dir] logfile '
    sys.exit(1)

  todir = ''
  if args[0] == '--todir':
    todir = args[1]
    del args[0:2]

  img_urls = read_urls(args[0])

  if todir:
    download_images(img_urls, todir)
  else:
    print '\n'.join(img_urls)

if __name__ == '__main__':
  main()

Exercício 7 - copyspecial.py

Download do Arquivo: copyspecial.py

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#!/usr/bin/python
# Copyright 2010 Google Inc.
# Licensed under the Apache License, Version 2.0
# http://www.apache.org/licenses/LICENSE-2.0

# Google's Python Class
# http://code.google.com/edu/languages/google-python-class/

import sys
import re
import os
import shutil
import commands

"""Copy Special exercise
"""

#The copyspecial.py program takes one or more directories as its arguments. We'll say that a #"special" file is one where the name contains the pattern __w__ somewhere, where the w is one or #more word chars. The provided main() includes code to parse the command line arguments, but the #rest is up to you. Write functions to implement the features below and modify main() to call your #functions.

# +++your code here+++
# Write functions and modify main() to call them

def get_special_paths(dir):  
"""
returns a list of the absolute paths of the special files in the given directory
"""

def copy_to(paths, dir): 
"""
given a list of paths, copies those files into the given director
"""

def zip_to(paths, zippath): 
"""
given a list of paths, zip those files up into the given zipfile 
Command to zip files:  zip -j zipfilename.zip file1 file2 file3...
"""


def main():
  # This basic command line argument parsing code is provided.
  # Add code to call your functions below.

  # Make a list of command line arguments, omitting the [0] element
  # which is the script itself.
  args = sys.argv[1:]
  if not args:
    print "usage: [--todir dir][--tozip zipfile] dir [dir ...]";
    sys.exit(1)

  # todir and tozip are either set from command line
  # or left as the empty string.
  # The args array is left just containing the dirs.
  todir = ''
  if args[0] == '--todir':
    todir = args[1]
    del args[0:2]

  tozip = ''
  if args[0] == '--tozip':
    tozip = args[1]
    del args[0:2]

  if len(args) == 0:
    print "error: must specify one or more dirs"
    sys.exit(1)

  # +++your code here+++
  # Call your functions
  
if __name__ == "__main__":
  main()

Soluções

Exercício 1 - list1.py

Download do Arquivo: list1.py

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#!/usr/bin/python -tt
# Copyright 2010 Google Inc.
# Licensed under the Apache License, Version 2.0
# http://www.apache.org/licenses/LICENSE-2.0

# Google's Python Class
# http://code.google.com/edu/languages/google-python-class/

# Basic list exercises
# Fill in the code for the functions below. main() is already set up
# to call the functions with a few different inputs,
# printing 'OK' when each function is correct.
# The starter code for each function includes a 'return'
# which is just a placeholder for your code.
# It's ok if you do not complete all the functions, and there
# are some additional functions to try in list2.py.

# A. match_ends
# Given a list of strings, return the count of the number of
# strings where the string length is 2 or more and the first
# and last chars of the string are the same.
# Note: python does not have a ++ operator, but += works.
def match_ends(words):
  # +++your code here+++
  # LAB(begin solution)
  count = 0
  for word in words:
    if len(word) >= 2 and word[0] == word[-1]:
      count = count + 1
  return count
  # LAB(replace solution)
  # return
  # LAB(end solution)


# B. front_x
# Given a list of strings, return a list with the strings
# in sorted order, except group all the strings that begin with 'x' first.
# e.g. ['mix', 'xyz', 'apple', 'xanadu', 'aardvark'] yields
# ['xanadu', 'xyz', 'aardvark', 'apple', 'mix']
# Hint: this can be done by making 2 lists and sorting each of them
# before combining them.
def front_x(words):
  # +++your code here+++
  # LAB(begin solution)
  # Put each word into the x_list or the other_list.
  x_list = []
  other_list = []
  for w in words:
    if w.startswith('x'):
      x_list.append(w)
    else:
      other_list.append(w)
  return sorted(x_list) + sorted(other_list)
  # LAB(replace solution)
  # return
  # LAB(end solution)


# LAB(begin solution)
# Extract the last element from a tuple -- used for custom sorting below.
def last(a):
  return a[-1]
# LAB(end solution)

# C. sort_last
# Given a list of non-empty tuples, return a list sorted in increasing
# order by the last element in each tuple.
# e.g. [(1, 7), (1, 3), (3, 4, 5), (2, 2)] yields
# [(2, 2), (1, 3), (3, 4, 5), (1, 7)]
# Hint: use a custom key= function to extract the last element form each tuple.
def sort_last(tuples):
  # +++your code here+++
  # LAB(begin solution)
  return sorted(tuples, key=last)
  # LAB(replace solution)
  # return
  # LAB(end solution)


# Simple provided test() function used in main() to print
# what each function returns vs. what it's supposed to return.
def test(got, expected):
  if got == expected:
    prefix = ' OK '
  else:
    prefix = '  X '
  print '%s got: %s expected: %s' % (prefix, repr(got), repr(expected))


# Calls the above functions with interesting inputs.
def main():
  print 'match_ends'
  test(match_ends(['aba', 'xyz', 'aa', 'x', 'bbb']), 3)
  test(match_ends(['', 'x', 'xy', 'xyx', 'xx']), 2)
  test(match_ends(['aaa', 'be', 'abc', 'hello']), 1)

  print
  print 'front_x'
  test(front_x(['bbb', 'ccc', 'axx', 'xzz', 'xaa']),
       ['xaa', 'xzz', 'axx', 'bbb', 'ccc'])
  test(front_x(['ccc', 'bbb', 'aaa', 'xcc', 'xaa']),
       ['xaa', 'xcc', 'aaa', 'bbb', 'ccc'])
  test(front_x(['mix', 'xyz', 'apple', 'xanadu', 'aardvark']),
       ['xanadu', 'xyz', 'aardvark', 'apple', 'mix'])

       
  print
  print 'sort_last'
  test(sort_last([(1, 3), (3, 2), (2, 1)]),
       [(2, 1), (3, 2), (1, 3)])
  test(sort_last([(2, 3), (1, 2), (3, 1)]),
       [(3, 1), (1, 2), (2, 3)])
  test(sort_last([(1, 7), (1, 3), (3, 4, 5), (2, 2)]),
       [(2, 2), (1, 3), (3, 4, 5), (1, 7)])


if __name__ == '__main__':
  main()

Exercício 2 - list2.py

Download do Arquivo: list2.py

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#!/usr/bin/python -tt
# Copyright 2010 Google Inc.
# Licensed under the Apache License, Version 2.0
# http://www.apache.org/licenses/LICENSE-2.0

# Google's Python Class
# http://code.google.com/edu/languages/google-python-class/

# Additional basic list exercises

# D. Given a list of numbers, return a list where
# all adjacent == elements have been reduced to a single element,
# so [1, 2, 2, 3] returns [1, 2, 3]. You may create a new list or
# modify the passed in list.
def remove_adjacent(nums):
  # +++your code here+++
  # LAB(begin solution)
  result = []
  for num in nums:
    if len(result) == 0 or num != result[-1]:
      result.append(num)
  return result
  # LAB(replace solution)
  # return
  # LAB(end solution)


# E. Given two lists sorted in increasing order, create and return a merged
# list of all the elements in sorted order. You may modify the passed in lists.
# Ideally, the solution should work in "linear" time, making a single
# pass of both lists.
def linear_merge(list1, list2):
  # +++your code here+++
  # LAB(begin solution)
  result = []
  # Look at the two lists so long as both are non-empty.
  # Take whichever element [0] is smaller.
  while len(list1) and len(list2):
    if list1[0] < list2[0]:
      result.append(list1.pop(0))
    else:
      result.append(list2.pop(0))

  # Now tack on what's left
  result.extend(list1)
  result.extend(list2)
  return result
  # LAB(replace solution)
  # return
  # LAB(end solution)

# Note: the solution above is kind of cute, but unforunately list.pop(0)
# is not constant time with the standard python list implementation, so
# the above is not strictly linear time.
# An alternate approach uses pop(-1) to remove the endmost elements
# from each list, building a solution list which is backwards.
# Then use reversed() to put the result back in the correct order. That
# solution works in linear time, but is more ugly.


# Simple provided test() function used in main() to print
# what each function returns vs. what it's supposed to return.
def test(got, expected):
  if got == expected:
    prefix = ' OK '
  else:
    prefix = '  X '
  print '%s got: %s expected: %s' % (prefix, repr(got), repr(expected))


# Calls the above functions with interesting inputs.
def main():
  print 'remove_adjacent'
  test(remove_adjacent([1, 2, 2, 3]), [1, 2, 3])
  test(remove_adjacent([2, 2, 3, 3, 3]), [2, 3])
  test(remove_adjacent([]), [])

  print
  print 'linear_merge'
  test(linear_merge(['aa', 'xx', 'zz'], ['bb', 'cc']),
       ['aa', 'bb', 'cc', 'xx', 'zz'])
  test(linear_merge(['aa', 'xx'], ['bb', 'cc', 'zz']),
       ['aa', 'bb', 'cc', 'xx', 'zz'])
  test(linear_merge(['aa', 'aa'], ['aa', 'bb', 'bb']),
       ['aa', 'aa', 'aa', 'bb', 'bb'])


if __name__ == '__main__':
  main()

Exercício 3 - string1.py

Download do Arquivo: string1.py

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#!/usr/bin/python -tt
# Copyright 2010 Google Inc.
# Licensed under the Apache License, Version 2.0
# http://www.apache.org/licenses/LICENSE-2.0

# Google's Python Class
# http://code.google.com/edu/languages/google-python-class/

# Basic string exercises
# Fill in the code for the functions below. main() is already set up
# to call the functions with a few different inputs,
# printing 'OK' when each function is correct.
# The starter code for each function includes a 'return'
# which is just a placeholder for your code.
# It's ok if you do not complete all the functions, and there
# are some additional functions to try in string2.py.


# A. donuts
# Given an int count of a number of donuts, return a string
# of the form 'Number of donuts: <count>', where <count> is the number
# passed in. However, if the count is 10 or more, then use the word 'many'
# instead of the actual count.
# So donuts(5) returns 'Number of donuts: 5'
# and donuts(23) returns 'Number of donuts: many'
def donuts(count):
  # +++your code here+++
  # LAB(begin solution)
  if count < 10:
    return 'Number of donuts: ' + str(count)
  else:
    return 'Number of donuts: many'
  # LAB(replace solution)
  # return
  # LAB(end solution)


# B. both_ends
# Given a string s, return a string made of the first 2
# and the last 2 chars of the original string,
# so 'spring' yields 'spng'. However, if the string length
# is less than 2, return instead the empty string.
def both_ends(s):
  # +++your code here+++
  # LAB(begin solution)
  if len(s) < 2:
    return ''
  first2 = s[0:2]
  last2 = s[-2:]
  return first2 + last2
  # LAB(replace solution)
  # return
  # LAB(end solution)


# C. fix_start
# Given a string s, return a string
# where all occurences of its first char have
# been changed to '*', except do not change
# the first char itself.
# e.g. 'babble' yields 'ba**le'
# Assume that the string is length 1 or more.
# Hint: s.replace(stra, strb) returns a version of string s
# where all instances of stra have been replaced by strb.
def fix_start(s):
  # +++your code here+++
  # LAB(begin solution)
  front = s[0]
  back = s[1:]
  fixed_back = back.replace(front, '*')
  return front + fixed_back
  # LAB(replace solution)
  # return
  # LAB(end solution)


# D. MixUp
# Given strings a and b, return a single string with a and b separated
# by a space '<a> <b>', except swap the first 2 chars of each string.
# e.g.
#   'mix', pod' -> 'pox mid'
#   'dog', 'dinner' -> 'dig donner'
# Assume a and b are length 2 or more.
def mix_up(a, b):
  # +++your code here+++
  # LAB(begin solution)
  a_swapped = b[:2] + a[2:]
  b_swapped = a[:2] + b[2:]
  return a_swapped + ' ' + b_swapped
  # LAB(replace solution)
  # return
  # LAB(end solution)


# Provided simple test() function used in main() to print
# what each function returns vs. what it's supposed to return.
def test(got, expected):
  if got == expected:
    prefix = ' OK '
  else:
    prefix = '  X '
  print '%s got: %s expected: %s' % (prefix, repr(got), repr(expected))


# Provided main() calls the above functions with interesting inputs,
# using test() to check if each result is correct or not.
def main():
  print 'donuts'
  # Each line calls donuts, compares its result to the expected for that call.
  test(donuts(4), 'Number of donuts: 4')
  test(donuts(9), 'Number of donuts: 9')
  test(donuts(10), 'Number of donuts: many')
  test(donuts(99), 'Number of donuts: many')

  print
  print 'both_ends'
  test(both_ends('spring'), 'spng')
  test(both_ends('Hello'), 'Helo')
  test(both_ends('a'), '')
  test(both_ends('xyz'), 'xyyz')

  
  print
  print 'fix_start'
  test(fix_start('babble'), 'ba**le')
  test(fix_start('aardvark'), 'a*rdv*rk')
  test(fix_start('google'), 'goo*le')
  test(fix_start('donut'), 'donut')

  print
  print 'mix_up'
  test(mix_up('mix', 'pod'), 'pox mid')
  test(mix_up('dog', 'dinner'), 'dig donner')
  test(mix_up('gnash', 'sport'), 'spash gnort')
  test(mix_up('pezzy', 'firm'), 'fizzy perm')


# Standard boilerplate to call the main() function.
if __name__ == '__main__':
  main()

Exercício 4 - string2.py

Download do Arquivo: string2.py

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#!/usr/bin/python2.4 -tt
# Copyright 2010 Google Inc.
# Licensed under the Apache License, Version 2.0
# http://www.apache.org/licenses/LICENSE-2.0

# Google's Python Class
# http://code.google.com/edu/languages/google-python-class/

# Additional basic string exercises

# D. verbing
# Given a string, if its length is at least 3,
# add 'ing' to its end.
# Unless it already ends in 'ing', in which case
# add 'ly' instead.
# If the string length is less than 3, leave it unchanged.
# Return the resulting string.
def verbing(s):
  # +++your code here+++
  # LAB(begin solution)
  if len(s) >= 3:
    if s[-3:] != 'ing': s = s + 'ing'
    else: s = s + 'ly'
  return s
  # LAB(replace solution)
  # return
  # LAB(end solution)


# E. not_bad
# Given a string, find the first appearance of the
# substring 'not' and 'bad'. If the 'bad' follows
# the 'not', replace the whole 'not'...'bad' substring
# with 'good'.
# Return the resulting string.
# So 'This dinner is not that bad!' yields:
# This dinner is good!
def not_bad(s):
  # +++your code here+++
  # LAB(begin solution)
  n = s.find('not')
  b = s.find('bad')
  if n != -1 and b != -1 and b > n:
    s = s[:n] + 'good' + s[b+3:]
  return s
  # LAB(replace solution)
  # return
  # LAB(end solution)


# F. front_back
# Consider dividing a string into two halves.
# If the length is even, the front and back halves are the same length.
# If the length is odd, we'll say that the extra char goes in the front half.
# e.g. 'abcde', the front half is 'abc', the back half 'de'.
# Given 2 strings, a and b, return a string of the form
#  a-front + b-front + a-back + b-back
def front_back(a, b):
  # +++your code here+++
  # LAB(begin solution)
  # Figure out the middle position of each string.
  a_middle = len(a) / 2
  b_middle = len(b) / 2
  if len(a) % 2 == 1:  # add 1 if length is odd
    a_middle = a_middle + 1
  if len(b) % 2 == 1:
    b_middle = b_middle + 1 
  return a[:a_middle] + b[:b_middle] + a[a_middle:] + b[b_middle:]
  # LAB(replace solution)
  # return
  # LAB(end solution)


# Simple provided test() function used in main() to print
# what each function returns vs. what it's supposed to return.
def test(got, expected):
  if got == expected:
    prefix = ' OK '
  else:
    prefix = '  X '
  print '%s got: %s expected: %s' % (prefix, repr(got), repr(expected))


# main() calls the above functions with interesting inputs,
# using the above test() to check if the result is correct or not.
def main():
  print 'verbing'
  test(verbing('hail'), 'hailing')
  test(verbing('swiming'), 'swimingly')
  test(verbing('do'), 'do')

  print
  print 'not_bad'
  test(not_bad('This movie is not so bad'), 'This movie is good')
  test(not_bad('This dinner is not that bad!'), 'This dinner is good!')
  test(not_bad('This tea is not hot'), 'This tea is not hot')
  test(not_bad("It's bad yet not"), "It's bad yet not")

  print
  print 'front_back'
  test(front_back('abcd', 'xy'), 'abxcdy')
  test(front_back('abcde', 'xyz'), 'abcxydez')
  test(front_back('Kitten', 'Donut'), 'KitDontenut')

if __name__ == '__main__':
  main()

Exercício 5 - wordcount.py

Download do Arquivo: wordcount.py

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#!/usr/bin/python -tt
# Copyright 2010 Google Inc.
# Licensed under the Apache License, Version 2.0
# http://www.apache.org/licenses/LICENSE-2.0

# Google's Python Class
# http://code.google.com/edu/languages/google-python-class/

"""Wordcount exercise
Google's Python class

The main() below is already defined and complete. It calls print_words()
and print_top() functions which you write.

1. For the --count flag, implement a print_words(filename) function that counts
how often each word appears in the text and prints:
word1 count1
word2 count2
...

Print the above list in order sorted by word (python will sort punctuation to
come before letters -- that's fine). Store all the words as lowercase,
so 'The' and 'the' count as the same word.

2. For the --topcount flag, implement a print_top(filename) which is similar
to print_words() but which prints just the top 20 most common words sorted
so the most common word is first, then the next most common, and so on.

Use str.split() (no arguments) to split on all whitespace.

Workflow: don't build the whole program at once. Get it to an intermediate
milestone and print your data structure and sys.exit(0).
When that's working, try for the next milestone.

Optional: define a helper function to avoid code duplication inside
print_words() and print_top().

"""

import sys

# +++your code here+++
# Define print_words(filename) and print_top(filename) functions.
# You could write a helper utility function that reads a file
# and builds and returns a word/count dict for it.
# Then print_words() and print_top() can just call the utility function.

#### LAB(begin solution)

def word_count_dict(filename):
  """Returns a word/count dict for this filename."""
  # Utility used by count() and Topcount().
  word_count = {}  # Map each word to its count
  input_file = open(filename, 'r')
  for line in input_file:
    words = line.split()
    for word in words:
      word = word.lower()
      # Special case if we're seeing this word for the first time.
      if not word in word_count:
        word_count[word] = 1
      else:
        word_count[word] = word_count[word] + 1
  input_file.close()  # Not strictly required, but good form.
  return word_count


def print_words(filename):
  """Prints one per line '<word> <count>' sorted by word for the given file."""
  word_count = word_count_dict(filename)
  words = sorted(word_count.keys())
  for word in words:
    print word, word_count[word]


def get_count(word_count_tuple):
  """Returns the count from a dict word/count tuple  -- used for custom sort."""
  return word_count_tuple[1]


def print_top(filename):
  """Prints the top count listing for the given file."""
  word_count = word_count_dict(filename)

  # Each item is a (word, count) tuple.
  # Sort them so the big counts are first using key=get_count() to extract count.
  items = sorted(word_count.items(), key=get_count, reverse=True)

  # Print the first 20
  for item in items[:20]:
    print item[0], item[1]

##### LAB(end solution)


# This basic command line argument parsing code is provided and
# calls the print_words() and print_top() functions which you must define.
def main():
  if len(sys.argv) != 3:
    print 'usage: ./wordcount.py {--count | --topcount} file'
    sys.exit(1)

  option = sys.argv[1]
  filename = sys.argv[2]
  if option == '--count':
    print_words(filename)
  elif option == '--topcount':
    print_top(filename)
  else:
    print 'unknown option: ' + option
    sys.exit(1)

if __name__ == '__main__':
  main()

Exercício 6 - logpuzzle.py

Download do Arquivo: logpuzzle.py

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#!/usr/bin/python
# Copyright 2010 Google Inc.
# Licensed under the Apache License, Version 2.0
# http://www.apache.org/licenses/LICENSE-2.0

# Google's Python Class
# http://code.google.com/edu/languages/google-python-class/

import os
import re
import sys
import urllib

"""Logpuzzle exercise
Given an apache logfile, find the puzzle urls and download the images.

Here's what a puzzle url looks like:
10.254.254.28 - - [06/Aug/2007:00:13:48 -0700] "GET /~foo/puzzle-bar-aaab.jpg HTTP/1.0" 302 528 "-" "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.6) Gecko/20070725 Firefox/2.0.0.6"
"""

# LAB(begin solution)
def url_sort_key(url):
  """Used to order the urls in increasing order by 2nd word if present."""
  match = re.search(r'-(\w+)-(\w+)\.\w+', url)
  if match:
    return match.group(2)
  else:
    return url
# LAB(end solution)

def read_urls(filename):
  """Returns a list of the puzzle urls from the given log file,
  extracting the hostname from the filename itself.
  Screens out duplicate urls and returns the urls sorted into
  increasing order."""
  # +++your code here+++
  # LAB(begin solution)
  # Extract the hostname from the filename
  underbar = filename.index('_')
  host = filename[underbar + 1:]

  # Store the ulrs into a dict to screen out the duplicates
  url_dict = {}

  f = open(filename)
  for line in f:
    # Find the path which is after the GET and surrounded by spaces.
    match = re.search(r'"GET (\S+)', line)
    # Above uses \S (upper case S) which is any non-space char
    # Alternately could use square brackets: "GET ([^ ]+)"
    # or the ? form: "GET (.+?) "

    if match:
      path = match.group(1)
      # Add to dict if it's a special "puzzle" url
      # (could combine this 'puzzle' check with the above GET extraction)
      if 'puzzle' in path:
        url_dict['http://' + host + path] = 1

  return sorted(url_dict.keys(), key=url_sort_key)
  # LAB(end solution)


def download_images(img_urls, dest_dir):
  """Given the urls already in the correct order, downloads
  each image into the given directory.
  Gives the images local filenames img0, img1, and so on.
  Creates an index.html in the directory
  with an img tag to show each local image file.
  Creates the directory if necessary.
  """
  # +++your code here+++
  # LAB(begin solution)
  if not os.path.exists(dest_dir):
    os.makedirs(dest_dir)

  index = file(os.path.join(dest_dir, 'index.html'), 'w')
  index.write('<html><body>\n')

  i = 0
  for img_url in img_urls:
    local_name = 'img%d' % i
    print 'Retrieving...', img_url
    urllib.urlretrieve(img_url, os.path.join(dest_dir, local_name))

    index.write('<img src="%s">' % (local_name,))
    i += 1

  index.write('\n</body></html>\n')
  index.close()
  # LAB(end solution)


def main():
  args = sys.argv[1:]

  if not args:
    print 'usage: [--todir dir] logfile '
    sys.exit(1)

  todir = ''
  if args[0] == '--todir':
    todir = args[1]
    del args[0:2]

  img_urls = read_urls(args[0])

  if todir:
    download_images(img_urls, todir)
  else:
    print '\n'.join(img_urls)

if __name__ == '__main__':
  main()

Exercício 7 - copyspecial.py

Download do Arquivo: copyspecial.py

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#!/usr/bin/python
# Copyright 2010 Google Inc.
# Licensed under the Apache License, Version 2.0
# http://www.apache.org/licenses/LICENSE-2.0

# Google's Python Class
# http://code.google.com/edu/languages/google-python-class/

import sys
import re
import os
import shutil
import commands

"""Copy Special exercise
"""

# +++your code here+++
# Write functions and modify main() to call them

# LAB(begin solution)
def get_special_paths(dirname):
  """Given a dirname, returns a list of all its special files."""
  result = []
  paths = os.listdir(dirname)  # list of paths in that dir
  for fname in paths:
    match = re.search(r'__(\w+)__', fname)
    if match:
      result.append(os.path.abspath(os.path.join(dirname, fname)))
  return result


def copy_to(paths, to_dir):
  """Copy all of the given files to the given dir, creating it if necessary."""
  if not os.path.exists(to_dir):
    os.mkdir(to_dir)
  for path in paths:
    fname = os.path.basename(path)
    shutil.copy(path, os.path.join(to_dir, fname))
    # could error out if already exists os.path.exists():


def zip_to(paths, zipfile):
  """Zip up all of the given files into a new zip file with the given name."""
  cmd = 'zip -j ' + zipfile + ' ' + ' '.join(paths)
  print "Command I'm going to do:" + cmd
  (status, output) = commands.getstatusoutput(cmd)
  # If command had a problem (status is non-zero),
  # print its output to stderr and exit.
  if status:
    sys.stderr.write(output)
    sys.exit(1)

# LAB(end solution)


def main():
  # This basic command line argument parsing code is provided.
  # Add code to call your functions below.

  # Make a list of command line arguments, omitting the [0] element
  # which is the script itself.
  args = sys.argv[1:]
  if not args:
    print "usage: [--todir dir][--tozip zipfile] dir [dir ...]";
    sys.exit(1)

  # todir and tozip are either set from command line
  # or left as the empty string.
  # The args array is left just containing the dirs.
  todir = ''
  if args[0] == '--todir':
    todir = args[1]
    del args[0:2]

  tozip = ''
  if args[0] == '--tozip':
    tozip = args[1]
    del args[0:2]

  if len(args) == 0:
    print "error: must specify one or more dirs"
    sys.exit(1)

  # +++your code here+++
  # Call your functions
  # LAB(begin solution)

  # Gather all the special files
  paths = []
  for dirname in args:
    paths.extend(get_special_paths(dirname))

  if todir:
    copy_to(paths, todir)
  elif tozip:
    zip_to(paths, tozip)
  else:
    print '\n'.join(paths)
  # LAB(end solution)

if __name__ == "__main__":
  main()