AttributeError: 'str' object has no attribute 'mean_validation_score'

Question

This error occurs in my code: AttributeError: 'str' object has no attribute 'mean_validation_score'. What can I do to resolve it?

def report(grid_scores, n_top=3):
    top_scores = sorted(grid_scores, key=itemgetter(1), reverse=True)[:n_top]
    for i, score in enumerate(top_scores):
        print("Rank: {0}".format(i + 1))
        print("Mean validation score: {0:.3f} (std: {1:.3f})".format(
              score.mean_validation_score,
              np.std(score.cv_validation_scores)))
        print("Parameters: {0}".format(score.parameters))
        print("")
report(clf.cv_results_)

Can you include what `grid_scores` is with some dummy data ? Im guessing its `clf.grid_scores_` from sklearn library ? If so please show us the cross validation code. — DollarAkshay, Jan 05 '19 at 16:24
can you try with: `sorted(grid_scores.items(), key=itemgetter(1), reverse=True)[:n_top]` to be `grid_scores` looks like a dict and you are trying to sort it by values. — YOLO, Jan 05 '19 at 16:52
you mean to replace sorted(grid_scores.items(), key=itemgetter(1), reverse=True)[:n_top] by grid_scores?? — user9010401, Jan 05 '19 at 16:55

Patrick Artner · Answer 1 · 2019-09-20T08:30:19.797

The error is quite clear: AttributeError: 'str' object has no attribute 'mean_validation_score'

There is only one place you use mean_validation_score and the object you use it on is a string - not what you think it is. string does not support the method you use on it - hence the error:

    for i, score in enumerate(top_scores):                              # score from here
        print("Rank: {0}".format(i + 1))
        print("Mean validation score: {0:.3f} (std: {1:.3f})".format(
              score.mean_validation_score,                              # usage here
              np.std(score.cv_validation_scores)))

Obviosly the top_scores is a iterable of type string - hence when you enumerate it

for i, score in enumerate(top_scores):

it produces indexes i and strings score.

You can resolve it by debugging your code:

top_scores = sorted(grid_scores, key=itemgetter(1), reverse=True)[:n_top]

and see why there are strings in it - fix that so it contains the objects that have .mean_validation_score and the error vanishes.

Helpful:

AttributeError: 'str' object has no attribute 'mean_validation_score'

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