非参数检验-Mann-Whitney U

def solve():
    import numpy as np
    from sklearn.datasets import load_iris
    iris = load_iris()
    X = iris.data
    y = iris.target
    # 双因素：使用sepal length和sepal width作为因素（分组）
    import statsmodels.api as sm
    import pandas as pd
    df = pd.DataFrame(____)
    df['____'] = y
    # 简化：输出各组均值个数
    print(len(df.groupby(____)['____'].mean()))