Question

我正尝试在数据框架上构建一个新列，如下所示：

l = [(2, 1), (1,1)]
df = spark.createDataFrame(l)

def calc_dif(x,y):
    if (x>y) and (x==1):
        return x-y

dfNew = df.withColumn("calc", calc_dif(df["_1"], df["_2"]))
dfNew.show()

但是，我明白了：

Traceback (most recent call last):
  File "/tmp/zeppelin_pyspark-2807412651452069487.py", line 346, in <module>
Exception: Traceback (most recent call last):
  File "/tmp/zeppelin_pyspark-2807412651452069487.py", line 334, in <module>
  File "<stdin>", line 38, in <module>
  File "<stdin>", line 36, in calc_dif
  File "/usr/hdp/current/spark2-client/python/pyspark/sql/column.py", line 426, in __nonzero__
    raise ValueError("Cannot convert column into bool: please use '&' for 'and', '|' for 'or', "
ValueError: Cannot convert column into bool: please use '&' for 'and', '|' for 'or', '~' for 'not' when building DataFrame boolean expressions.

为什么会这样？我该如何解决？

Answer 1

使用udf：

from pyspark.sql.functions import udf

@udf("integer")
def calc_dif(x,y):
    if (x>y) and (x==1):
        return x-y

或（推荐）时的情况

from pyspark.sql.functions import when

def calc_dif(x,y):
    when(( x > y) & (x == 1), x - y)

第一个计算Python对象，第二个计算Spark Columns

Answer 2

抱怨是因为您为calc_dif函数提供了整个列对象，而不是相应行的实际数据。您需要使用udf来包装calc_dif函数：

from pyspark.sql.types import IntegerType
from pyspark.sql.functions import udf

l = [(2, 1), (1,1)]
df = spark.createDataFrame(l)

def calc_dif(x,y):
    # using the udf the calc_dif is called for every row in the dataframe
    # x and y are the values of the two columns 
    if (x>y) and (x==1):
        return x-y

udf_calc = udf(calc_dif, IntegerType())

dfNew = df.withColumn("calc", udf_calc("_1", "_2"))
dfNew.show()

# since x < y calc_dif returns None
+---+---+----+
| _1| _2|calc|
+---+---+----+
|  2|  1|null|
|  1|  1|null|
+---+---+----+

Answer 3

对于有类似错误的任何人：当我需要一个Pandas对象并遇到相同的错误时，我试图传递rdd。显然，我可以通过“ .toPandas（）”来解决它

Answer 4

对于遇到相同错误消息的任何人，请检查括号。有时布尔表达式需要更具体的表达式，例如;

DF_New= 
df1.withColumn('EventStatus',\
                  F.when(((F.col("Adjusted_Timestamp")) <\
                          (F.col("Event_Finish"))) &\
                         ((F.col("Adjusted_Timestamp"))>\ 
                           F.col("Event_Start"))),1).otherwise(0))

ValueError：无法将列转换为bool

4 个答案: