统计平台评分分布与低评分商家排行

def solve():
    from pyodide.http import open_url
    from io import StringIO
    import pandas as pd
    reviews=pd.read_csv(StringIO(open_url("https://data.zuihe.com/dbd/ms-takeaway/state_04/reviews.csv").read()))
    print(f"Total reviews: {len(reviews)}")
    print(f"Avg merchant_rating: {round(reviews['merchant_rating'].mean(),2)}")
    print(f"1-star reviews: {len(reviews[reviews['merchant_rating']==1])}")
    print(f"5-star reviews: {len(reviews[reviews['merchant_rating']==5])}")
    by_merchant=reviews.groupby('merchant_id')['merchant_rating'].mean().round(2).nsmallest(5)
    print("Lowest rated merchants (avg):")
    for mid,avg in by_merchant.items():
        print(f"  {mid}: {avg}")