sklearn.datasets.load_breast_cancer(*, return_X_y=False, as_frame=False)[source]

Load and return the breast cancer wisconsin dataset (classification).

The breast cancer dataset is a classic and very easy binary classification dataset.



Samples per class


Samples total





real, positive

Read more in the User Guide.

return_X_ybool, default=False

If True, returns (data, target) instead of a Bunch object. See below for more information about the data and target object.

New in version 0.18.

as_framebool, default=False

If True, the data is a pandas DataFrame including columns with appropriate dtypes (numeric). The target is a pandas DataFrame or Series depending on the number of target columns. If return_X_y is True, then (data, target) will be pandas DataFrames or Series as described below.

New in version 0.23.


Dictionary-like object, with the following attributes.

data{ndarray, dataframe} of shape (569, 30)

The data matrix. If as_frame=True, data will be a pandas DataFrame.

target: {ndarray, Series} of shape (569,)

The classification target. If as_frame=True, target will be a pandas Series.

feature_names: list

The names of the dataset columns.

target_names: list

The names of target classes.

frame: DataFrame of shape (569, 31)

Only present when as_frame=True. DataFrame with data and target.

New in version 0.23.

DESCR: str

The full description of the dataset.

filename: str

The path to the location of the data.

New in version 0.20.

(data, target)tuple if return_X_y is True

New in version 0.18.

The copy of UCI ML Breast Cancer Wisconsin (Diagnostic) dataset is
downloaded from:


Let’s say you are interested in the samples 10, 50, and 85, and want to know their class name.

>>> from sklearn.datasets import load_breast_cancer
>>> data = load_breast_cancer()
>>>[[10, 50, 85]]
array([0, 1, 0])
>>> list(data.target_names)
['malignant', 'benign']