Assaf Mendelson created SPARK-17333:
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Summary: Make pyspark interface friendly with static analysis
Key: SPARK-17333
URL: https://issues.apache.org/jira/browse/SPARK-17333
Project: Spark
Issue Type: Improvement
Components: PySpark
Reporter: Assaf Mendelson
Priority: Trivial
Static analysis tools such as those common to IDE for auto completion and error
marking, tend to have poor results with pyspark.
This is cause by two separate issues:
The first is that many elements are created programmatically such as the max
function in pyspark.sql.functions.
The second is that we tend to use pyspark in a functional manner, meaning that
we chain many actions (e.g. df.filter().groupby().agg()....) and since python
has no type information this can become difficult to understand.
I would suggest changing the interface to improve it.
The way I see it we can either change the interface or provide interface
enhancements.
Changing the interface means defining (when possible) all functions directly,
i.e. instead of having a __functions__ dictionary in pyspark.sql.functions.py
and then generating the functions programmatically by using _create_function,
create the function directly.
def max(col):
"""
docstring
"""
_create_function(max,"docstring")
Second we can add type indications to all functions as defined in pep 484 or
pycharm's legacy type hinting
(https://www.jetbrains.com/help/pycharm/2016.1/type-hinting-in-pycharm.html#legacy).
So for example max might look like this:
def max(col):
"""
does a max.
:type col: Column
:rtype Column
"""
This would provide a wide range of support as these types of hints, while old
are pretty common.
A second option is to use PEP 3107 to define interfaces (pyi files)
in this case we might have a functions.pyi file which would contain something
like:
def max(col: Column) -> Column:
"""
Aggregate function: returns the maximum value of the expression in a group.
"""
...
This has the advantage of easier to understand types and not touching the code
(only supported code) but has the disadvantage of being separately managed
(i.e. greater chance of doing a mistake) and the fact that some configuration
would be needed in the IDE/static analysis tool instead of working out of the
box.
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