练习1
#!/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<10: return "Number of donuts: "+str(count) else: 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 s[:2]+s[-2:] else: 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 # Hint: s.replace(stra, strb) returns a version of string s # where all instances of stra have been replaced by strb.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 s[0]+s.replace(s[0],'*')[1:] # 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 a.replace(a[:2],b[:2])+" "+b.replace(b[:2],a[:2]) # 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()
练习2
#!/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 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+++ if len(s) < 3 : return s elif s.endswith('ing') : return s+'ly' else : return s+'ing' 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+++ not_p=s.find('not') bad_p=s.find('bad') if not_p>bad_p: return s else: return s.replace(s[not_p:bad_p+3],'good') 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+++ a_odd=len(a)%2 b_odd=len(b)%2 if a_odd: a_front=a[:len(a)//2+1] a_back=a[len(a)//2+1:] else: a_front=a[:len(a)//2] a_back=a[len(a)//2:] if b_odd: b_front=b[:len(b)//2+1] b_back=b[len(b)//2+1:] else: b_front=b[:len(b)//2] b_back=b[len(b)//2:] return a_front + b_front + a_back + b_back # 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()