new_contents: #!/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):
    text = 'Number of donuts: %s'
    if count >= 10:
      text = text % 'many'
    else:
      text = text % str(count)
    return text
  
  
  # 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):
    i = len(s)
    if i < 2: return ''
    else: return s[0:2]+s[-2:]
  
  
  
  # 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  # where all instances of stra have been replaced by strb.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):
    return s[0] + s[1:].replace(s[0], '*')
  
  
  # 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):
    a_new = b[:2] + a[2:]
    b_new = a[:2] + b[2:]
    return a_new + " " + b_new
  
  # 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()
  
  
subject: Create string1.py