google python class exercise

谷歌 python class 地址 ： https://developers.google.com/edu/python/

美国名字： http://www.socialsecurity.gov/OACT/babynames/

1 string1.py

string 拼接的时候，比较难搞

c = a + b 这种方式不能用，不知道为什么！！！

#!/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+++if count <= 9: return "Number of donuts: %d" % countelse:return "Number of donuts: many"# 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+++if len(s)<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is length 1 or more.# Hint: s.replace(stra, strb) returns a version of string s# where all instances of stra have been replaced by strb.def fix_start(s):  # +++your code here+++first_char = s[0]repl = s.replace(s[0], "*")s = s[0] + repl[1:]return s# D. MixUp# Given strings a and b, return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+++a_tmp = a[0:2] + b[2:]b_tmp = b[0:2] + a[2:]return_tmp = "%s %s" % (b_tmp, a_tmp)return return_tmp# 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()

2，list 

#!/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+++match_cnt = 0for var in words:if len(var)>=2:if var[0] == var[-1]:match_cnt += 1return match_cnt# 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+++words_z=[];words_abc=[];for var in words:if var[0] == "x":words_z.append(var)else :words_abc.append(var)return sorted(words_z) + sorted(words_abc)#words_abc = sorted(words_abc)#print words_abc#words_z = sorted(words_z)#print words_z#words_z.extend(words_abc)#print words_z#return words_z# 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 Last_char(s):return s[-1]def sort_last(tuples):  # +++your code here+++  return sorted(tuples, key=Last_char)# 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()