spark.DataFrane分布式转pandas.dataframe

import pandas as pd
def _map_to_pandas(rdds):
    return [pd.DataFrame(list(rdds))]
    
def topas(df, n_partitions=None):
    if n_partitions is not None: df = df.repartition(n_partitions)
    df_pand = df.rdd.mapPartitions(_map_to_pandas).collect()
    df_pand = pd.concat(df_pand)
    df_pand.columns = df.columns
    return df_pand
    
pandas_df = topas(spark_df)