KNN分类器训练与评估

def solve():
    import pandas as pd
    from sklearn.neighbors import KNeighborsClassifier
    from sklearn.model_selection import train_test_split
    df = pd.read_csv("https://data.zuihe.com/iris.csv")
    X = df.drop("species", axis=1); y = df["species"]
    X_train, X_test, y_train, y_test = train_test_split(X, y, random_state=42)
    knn = KNeighborsClassifier(n_neighbors=3)
    knn.fit(X_train, y_train)
    print(f"{knn.score(X_test, y_test):.2f}")