AttributeError: 'list' object has no attribute 'copy'

Question

I have the following code snippet

classifier = NaiveBayesClassifier.train(train_data)
#classifier.show_most_informative_features(n=20)
results = classifier.classify(test_data)

and the error shows in the following line

results = classifier.classify(test_data)

error:

Traceback (most recent call last):
  File "trial_trial.py", line 46, in <module>
    results = classifier.classify(test_data)
  File "c:\Users\Amr\Anaconda\lib\site-packages\nltk\classify\naivebayes.py", line 88, in classify
    return self.prob_classify(featureset).max()
  File "c:\Users\Amr\Anaconda\lib\site-packages\nltk\classify\naivebayes.py", line 94, in prob_classify
    featureset = featureset.copy()
AttributeError: 'list' object has no attribute 'copy'

I think of extending base class list in python and add copy function but I'm not expert in python and I don't know how to solve this problem.

Answer 1

The list.copy method does not work both in python 2.x and python 3.x, I wonder why it is still in the documentation. To achieve the results of copying a list, user the list keyword:

fruits = ['banana', 'cucumber', 'apple', 'water mellon']
my_fruits = list(fruits)

Optionally, you can copy a list by slicing it:

my_fruits_copy = fruits[:]