python使用spark_python – 如何添加一个新的列到Spark DataFrame(使用PySpark)？

您不能在Spark中为DataFrame添加任意列。只能通过使用文字创建新列(其他文字类型在

How to add a constant column in a Spark DataFrame?中描述)

from pyspark.sql.functions import lit

df = sqlContext.createDataFrame(

[(1, "a", 23.0), (3, "B", -23.0)], ("x1", "x2", "x3"))

df_with_x4 = df.withColumn("x4", lit(0))

df_with_x4.show()

## +---+---+-----+---+

## | x1| x2| x3| x4|

## +---+---+-----+---+

## | 1| a| 23.0| 0|

## | 3| B|-23.0| 0|

## +---+---+-----+---+

转换现有列：

from pyspark.sql.functions import exp

df_with_x5 = df_with_x4.withColumn("x5", exp("x3"))

df_with_x5.show()

## +---+---+-----+---+--------------------+

## | x1| x2| x3| x4| x5|

## +---+---+-----+---+--------------------+

## | 1| a| 23.0| 0| 9.744803446248903E9|

## | 3| B|-23.0| 0|1.026187963170189...|

## +---+---+-----+---+--------------------+

包括使用join：

from pyspark.sql.functions import exp

lookup = sqlContext.createDataFrame([(1, "foo"), (2, "bar")], ("k", "v"))

df_with_x6 = (df_with_x5

.join(lookup, col("x1") == col("k"), "leftouter")

.drop("k")

.withColumnRenamed("v", "x6"))

## +---+---+-----+---+--------------------+----+

## | x1| x2| x3| x4| x5| x6|

## +---+---+-----+---+--------------------+----+

## | 1| a| 23.0| 0| 9.744803446248903E9| foo|

## | 3| B|-23.0| 0|1.026187963170189...|null|

## +---+---+-----+---+--------------------+----+

或使用函数/ udf生成：

from pyspark.sql.functions import rand

df_with_x7 = df_with_x6.withColumn("x7", rand())

df_with_x7.show()

## +---+---+-----+---+--------------------+----+-------------------+

## | x1| x2| x3| x4| x5| x6| x7|

## +---+---+-----+---+--------------------+----+-------------------+

## | 1| a| 23.0| 0| 9.744803446248903E9| foo|0.41930610446846617|

## | 3| B|-23.0| 0|1.026187963170189...|null|0.37801881545497873|

## +---+---+-----+---+--------------------+----+-------------------+

性能方面，映射到Catalyst表达式的内置函数(pyspark.sql.functions)通常优于Python用户定义的函数。

如果你想添加任意RDD的内容作为列，你可以

>添加row numbers to existing data frame>在RDD上调用zipWithIndex并将其转换为数据帧>使用index作为连接键连接