Google’s Python Class – Review Pt 1

I have started watching Google’s Python Class – http://code.google.com/edu/languages/google-python-class/

So far, I have covered the first lecture video, and at the end we were required to complete string1.py & string2.py with the correct code to have all the functions return the proper data. Output and my code below.

string1.py output

MB-PR0:basic jgilmour$ python string1.py
donuts
OK got: ‘Number of donuts: 4′ expected: ‘Number of donuts: 4′
OK got: ‘Number of donuts: 9′ expected: ‘Number of donuts: 9′
OK got: ‘Number of donuts: many’ expected: ‘Number of donuts: many’
OK got: ‘Number of donuts: many’ expected: ‘Number of donuts: many’

both_ends
OK got: ‘spng’ expected: ‘spng’
OK got: ‘Helo’ expected: ‘Helo’
OK got: ” expected: ”
OK got: ‘xyyz’ expected: ‘xyyz’

fix_start
OK got: ‘ba**le’ expected: ‘ba**le’
OK got: ‘a*rdv*rk’ expected: ‘a*rdv*rk’
OK got: ‘goo*le’ expected: ‘goo*le’
OK got: ‘donut’ expected: ‘donut’

mix_up
OK got: ‘pox mid’ expected: ‘pox mid’
OK got: ‘dig donner’ expected: ‘dig donner’
OK got: ‘spash gnort’ expected: ‘spash gnort’
OK got: ‘fizzy perm’ expected: ‘fizzy perm’

string1.py code

MB-PR0:basic jgilmour$ cat string1.py 
#!/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):
	if count >= 10:
		numOfDonuts = 'Number of donuts: many'
	else:
		numOfDonuts = 'Number of donuts: ' + str(count)
	return numOfDonuts

# 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):
	if len(s) < 2:
		returnString = ''
	else:
		returnString = s[0:2] + s[-2:]
	return returnString

# 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):
	stringReturned = s[1:]
	stringReturned = s[0] + stringReturned.replace(s[0], '*')
	return stringReturned

# 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):
	tempA = a[0:2]
	tempB = b[0:2]
	stringA = a.replace(tempA, tempB)
	stringB = b.replace(tempB, tempA)
	return stringA + " " + stringB

# 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()

string2.py output:

MB-PR0:basic jgilmour$ python string2.py
verbing
OK got: ‘hailing’ expected: ‘hailing’
OK got: ‘swimingly’ expected: ‘swimingly’
OK got: ‘do’ expected: ‘do’

not_bad
OK got: ‘This movie is good’ expected: ‘This movie is good’
OK got: ‘This dinner is good!’ expected: ‘This dinner is good!’
OK got: ‘This tea is not hot’ expected: ‘This tea is not hot’
OK got: “It’s bad yet not” expected: “It’s bad yet not”

front_back
OK got: ‘abxcdy’ expected: ‘abxcdy’
OK got: ‘abcxydez’ expected: ‘abcxydez’
OK got: ‘KitDontenut’ expected: ‘KitDontenut’

string2.py code

MB-PR0:basic jgilmour$ cat string2.py 
#!/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):
	if len(s) > 3:
		if s[-3:] == 'ing':
			s = s + 'ly'
		else:
			s = s + 'ing'
	return s

# 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):
	locationOfNot = s.find('not')
	locationOfBad = s.find('bad')
	if locationOfBad > locationOfNot:
		s = s[:locationOfNot] + 'good' + s[locationOfBad+3:]
	return s

# 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):
# this could probably be a function, meh.
  if len(a)%2 == 1:
    afront = a[:(len(a)/2)+1]
    aback = a[(len(a)/2)+1:]
  if len(a)%2 == 0:
    afront = a[:(len(a)/2)]
    aback = a[(len(a)/2):]
  if len(b)%2 == 1:
    bfront = b[:(len(b)/2)+1]
    bback = b[(len(b)/2)+1:]
  if len(b)%2 == 0:
    bfront = b[:(len(b)/2)]
    bback = b[(len(b)/2):]
  return afront + bfront + aback + bback

# 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()