Pyspark dataframe how to drop rows with nulls in all columns?

问题

For a dataframe, before it is like:

+----+----+----+
|  ID|TYPE|CODE|
+----+----+----+
|   1|   B|  X1|
|null|null|null|
|null|   B|  X1|
+----+----+----+

After I hope it's like:

+----+----+----+
|  ID|TYPE|CODE|
+----+----+----+
|   1|   B|  X1|
|null|   B|  X1|
+----+----+----+

I prefer a general method such that it can apply when df.columns is very long. Thanks!

回答1:

One option is to use functools.reduce to construct the conditions:

from functools import reduce
df.filter(~reduce(lambda x, y: x & y, [df[c].isNull() for c in df.columns])).show()
+----+----+----+
|  ID|TYPE|CODE|
+----+----+----+
|   1|   B|  X1|
|null|   B|  X1|
+----+----+----+

where reduce produce a query as follows:

~reduce(lambda x, y: x & y, [df[c].isNull() for c in df.columns])
# Column<b'(NOT (((ID IS NULL) AND (TYPE IS NULL)) AND (CODE IS NULL)))'>

回答2:

Providing strategy for na.drop is all you need:

df = spark.createDataFrame([
    (1, "B", "X1"), (None, None, None), (None, "B", "X1"), (None, "C", None)],
    ("ID", "TYPE", "CODE")
)

df.na.drop(how="all").show()

+----+----+----+
|  ID|TYPE|CODE|
+----+----+----+  
|   1|   B|  X1|
|null|   B|  X1|
|null|   C|null|
+----+----+----+

Alternative formulation can be achieved with threshold (number of NOT NULL values):

df.na.drop(thresh=1).show()

+----+----+----+
|  ID|TYPE|CODE|
+----+----+----+
|   1|   B|  X1|
|null|   B|  X1|
|null|   C|null|
+----+----+----+

来源：https://stackoverflow.com/questions/48228909/pyspark-dataframe-how-to-drop-rows-with-nulls-in-all-columns