What’s the problem? The model is trained on the same data, but predicts nothing. An error appears

ValueError: The truth value of an array with more than one element is ambiguous.Use a.any () or a.all ()

Was saving data to DataFrame, but still error.

ValueError: The truth value of a DataFrame is ambiguous. Use a.empty, a.bool (), a.item (), a.any () or a.all ().

## Answer 1, authority 100%

The `dt.predict(X, check_input=True)`

method expects two arguments – a matrix of values from which predictions will be made and a `check_input`

boolean flag. You passed an array of valid values as the second parameter instead of a scalar value. In the code `dt.predict`

there is a check `if check_input:`

– an exception will be thrown on this line of code, because the construction `if np.array([1, 0, 0, 2])`

– cannot be unambiguously checked.

It makes no sense to pass the well-known answer to `dt.predict()`

– `y_test`

.

The correct way to do this:

```
predicted = dt.predict(X_test)
```

If you want to check the accuracy of predictions, you can use the `.score()`

:

```
In [5]: dt.score(X_test, y_test)
Out[5]: 0.9473684210526315
```