我正在尝试从O'Reilly的Python Cookbook（第2版）中实现一个配方，并且一小部分配方不能正常工作。我希望有人可以帮我找出原因。
配方是“5.14：使用评级功能增强字典类型”。我已经完成了大部分代码，但是在尝试更改密钥的“排名”时出现错误。我作为作者的所有评论都留下了，所以任何想要帮助的人都会对“底层”和“暗淡”的内容有所了解。特别是“_rating”方面，我认为它会以某种方式导致错误。
ERROR：
File "rating.py", line 119, in <module>
r["john"]=20
File "rating.py", line 40, in __setitem__
del self._rating[self.rating(k)] ##
AttributeError: 'Ratings' object has no attribute 'rating'
CODE：
class Ratings(UserDict.DictMixin, dict):
'''The implementation carefully mixes inheritance and delegation
to achieve reasonable performance while minimizing boilerplate,
and, of course, to ensure semantic correctness as above. All
mappings' methods not implemented below get inherited, mostly
from DictMixin, but, crucially!, __getitem__ from dict. '''
def __init__(self, *args, **kwds):
''' This class gets instantiated just like 'dict' '''
dict.__init__(self, *args, **kwds)
# self._rating is the crucial auxiliary data structure: a list
# of all (value, key) pairs, kept in "natural"ly-sorted order
self._rating = [ (v, k) for k, v in dict.iteritems(self) ]
self._rating.sort()
def copy(self):
''' Provide an identical but independent copy '''
return Ratings(self)
def __setitem__(self, k, v):
''' besides delegating to dict, we maintain self._rating '''
if k in self:
del self._rating[self.rating(k)] ##
dict.__setitem__(self, k, v)
insort_left(self._rating, (v, k))
def __delitem__(self, k):
''' besides delegating to dict, we maintain self._rating '''
del self._rating[self.rating(k)]
dict.__delitem__(self, k)
''' delegate some methods to dict explicitly to avoid getting
DictMixin's slower (though correct) implementations instead '''
__len__ = dict.__len__
__contains__ = dict.__contains__
has_key = __contains__
''' the key semantic connection between self._rating and the order
of self.keys( ) -- DictMixin gives us all other methods 'for
free', although we could implement them directly for slightly
better performance. '''
def __iter__(self):
for v, k in self._rating:
yield k
iterkeys = __iter__
def keys(self):
return list(self)
#the three ratings-related methods
def rating(self, key):
item = self[key], key
i = bisect_left(self._rating, item)
if item == self._rating[i]:
return i
raise LookUpError, "item not found in rating"
def getValueByRating(self, rating):
return self._rating[rating][0]
def getKeyByRating(self, rating):
return self._rating[rating][1]
def _test( ):
''' we use doctest to test this module, which must be named
rating.py, by validating all the examples in docstrings. '''
import doctest, rating
doctest.testmod(rating)
if __name__ == "__main__":
r = Ratings({"bob":30, "john":30})
print "r is"
print r
print "\n"
print "len(r) is"
print len(r)
print "\n"
print "updating with {'paul': 20, 'tom': 10} "
r.update({"paul": 20, "tom": 10})
print "\n"
print "now r is"
print r
print "\n"
print "r.has_key('paul') is"
print r.has_key("paul")
print "\n"
print " 'paul' in r is"
print ("paul" in r)
print "\n"
print "r.has_key('alex') is"
print r.has_key("alex")
print "\n"
print " 'alex' in r is"
print ("alex" in r)
print '\n'
print 'r is'
print r
print "changing john to '20' with 'r['john']= 20' doesn't work. "
r["john"]=20
答案 0 :(得分：1)
您的问题是缩进。您必须将以下块向左移动一级，才能将它们识别为类方法。
def __iter__(self):
for v, k in self._rating:
yield k
iterkeys = __iter__
def keys(self):
return list(self)
#the three ratings-related methods
def rating(self, key):
item = self[key], key
i = bisect_left(self._rating, item)
if item == self._rating[i]:
return i
raise LookUpError, "item not found in rating"
def getValueByRating(self, rating):
return self._rating[rating][0]
def getKeyByRating(self, rating):
return self._rating[rating][1]
def _test( ):
''' we use doctest to test this module, which must be named
rating.py, by validating all the examples in docstrings. '''
import doctest, rating
doctest.testmod(rating)
print "doc test?"
所以课程将是
class Ratings(UserDict.DictMixin, dict):
'''The implementation carefully mixes inheritance and delegation
to achieve reasonable performance while minimizing boilerplate,
and, of course, to ensure semantic correctness as above. All
mappings' methods not implemented below get inherited, mostly
from DictMixin, but, crucially!, __getitem__ from dict. '''
def __init__(self, *args, **kwds):
''' This class gets instantiated just like 'dict' '''
dict.__init__(self, *args, **kwds)
# self._rating is the crucial auxiliary data structure: a list
# of all (value, key) pairs, kept in "natural"ly-sorted order
self._rating = [ (v, k) for k, v in dict.iteritems(self) ]
self._rating.sort()
def copy(self):
''' Provide an identical but independent copy '''
return Ratings(self)
def __setitem__(self, k, v):
''' besides delegating to dict, we maintain self._rating '''
if k in self:
del self._rating[self.rating(k)] ##
dict.__setitem__(self, k, v)
insort_left(self._rating, (v, k))
def __delitem__(self, k):
''' besides delegating to dict, we maintain self._rating '''
del self._rating[self.rating(k)]
dict.__delitem__(self, k)
''' delegate some methods to dict explicitly to avoid getting
DictMixin's slower (though correct) implementations instead '''
__len__ = dict.__len__
__contains__ = dict.__contains__
has_key = __contains__
''' the key semantic connection between self._rating and the order
of self.keys( ) -- DictMixin gives us all other methods 'for
free', although we could implement them directly for slightly
better performance. '''
def __iter__(self):
for v, k in self._rating:
yield k
iterkeys = __iter__
def keys(self):
return list(self)
#the three ratings-related methods
def rating(self, key):
item = self[key], key
i = bisect_left(self._rating, item)
if item == self._rating[i]:
return i
raise LookUpError, "item not found in rating"
def getValueByRating(self, rating):
return self._rating[rating][0]
def getKeyByRating(self, rating):
return self._rating[rating][1]
def _test( ):
''' we use doctest to test this module, which must be named
rating.py, by validating all the examples in docstrings. '''
import doctest, rating
doctest.testmod(rating)
print "doc test?"
if __name__ == "__main__":
r = Ratings({"bob":30, "john":30})
print "r is"
print r
print "\n"
print "len(r) is"
print len(r)
print "\n"
print "updating with {'paul': 20, 'tom': 10} "
r.update({"paul": 20, "tom": 10})
print "\n"
print "now r is"
print r
print "\n"
print "r.has_key('paul') is"
print r.has_key("paul")
print "\n"
print " 'paul' in r is"
print ("paul" in r)
print "\n"
print "r.has_key('alex') is"
print r.has_key("alex")
print "\n"
print " 'alex' in r is"
print ("alex" in r)
print '\n'
print 'r is'
print r
print "changing john to '20' with 'r['john']= 20' doesn't work. "
r["john"]=20