断言错误：所有表达式都应该是列

Question

我加入了两个 PySpark DataFrames，如下所示：

exprs = [max(x) for x in ["col1","col2"]]
df = df1.union(df2).groupBy(['campk', 'ppk']).agg(*exprs)

但我收到此错误：

AssertionError: all exprs should be Column

怎么了？

Answer 1

exprs = [max(x) for x in ["col1","col2"]]

将返回具有最大 ASCII 值的字符，即 ['o', 'o']

引用正确的max会起作用：

>>> from pyspark.sql import functions as F
>>> exprs = [F.max(x) for x in ["col1","col2"]]
>>> print(exprs)
[Column<max(col1)>, Column<max(col2)>]