PySpark SQL Functions | count method
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PySpark SQL Functions' count(~) is an aggregate method used in conjunction with the agg(~) method to compute the number of items in each group.
Parameters
1. col | string or Column
The column to perform the count on.
Return Value
A new PySpark Column.
Examples
Consider the following PySpark DataFrame:
+-----+-----+| name|class|+-----+-----+| Alex| A|| Bob| B||Cathy| A|+-----+-----+
Counting the number of items in each group
To count the number of rows for each class group:
Here, note the following:
we are first grouping by the
classcolumn usinggroupBy(~), and then for each group, we are counting how many rows there are. Technically speaking, we are counting the number ofclassvalues in each group (F.count('class')), but this is equivalent to just counting the number of rows in each group.we are assigning a label to the resulting aggregate column using the
alias(~)method. Note that the default label assigned is'count'.
