Question

I have a pickled file called classifier.pkl that I am trying to load into another module. However, I get an error I don’t understand.

My code to pickle:

features = ['bob','ice','snowing'] #... shortened for exposition's sake
def extract_features(document):
      return  {'contains(%s)'% word: (word in set(document)) 
                 for word in all_together_word_list} 
training_set = classify.util.apply_features(extract_features,tweets[0])
classifier = NaiveBayesClassifier.train(training_set)
cPcikle.dump(open('cocaine_classifier.pkl','wb'))

My code to unpickle:

features, extract_features, classifier = 
         cPickle.load(open('cocaine_classifier.pkl','rb'))

My error:

AttributeError: 'module' object has no attribute 'extract_features'

A while ago I made the .pkl file by pickling three things:

• features : list
• extract_features : function
• classifier : instance of NLTK Naive Bayes Classifier

Puzzlingly, I get the same error with the following code:

x = cPickle.load(open('cocaine_classifier.pkl','rb'))

Why can’t I retrieve three things? Even when I’m not trying to unpack the tuple?

Update

As NPE pointed out the path of the function to be unpickled must exactly match the function into which its being unpickled. I was debugging and Terminal and so from mod import * loads everything into the namespace whereas import mod as m does not.

Answer 1

The problem is that when you pickle a function, only the (fully-qualified) name of the function is pickled, not the function itself. This means that you have to have the function definition in place when you’re unpickling.

Did you by any chance mean to pickle the result of calling extract_features?