pandas和spark的dataframe互轉

pandas的dataframe轉spark的dataframe

from pyspark.sql import SparkSession
# 初始化spark會話
spark = SparkSession \
    .builder \
    .getOrCreate()

spark_df = spark.createDataFrame(pandas_df)

spark的dataframe轉pandas的dataframe

import pandas as pd

pandas_df = spark_df.toPandas()

因爲pandas的方式是單機版的，即toPandas()的方式是單機版的，因此參考breeze_lsw改爲分佈式版本：

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)