交叉验证

def solve():
    import pandas as pd
    from sklearn.neighbors import KNeighborsClassifier
    from sklearn.model_selection import cross_val_score
    df = pd.read_csv("https://data.zuihe.com/iris.csv")
    X = df.drop("species", axis=1); y = df["species"]
    scores = cross_val_score(KNeighborsClassifier(5), X, y, cv=5)
    folds = ",".join(f"{s:.2f}" for s in scores)
    print(f"{folds};{scores.mean():.2f}")