add python unit test

tests/python/testcase/string3.py

@@ -0,0 +1,140 @@
+#!/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+# where all instances of stra have been replaced by strb.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()