[jira] [Updated] (SPARK-17333) Make pyspark interface friendly with mypy static analysis

["Hyukjin Kwon (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-17333?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Hyukjin Kwon updated SPARK-17333:
---------------------------------
    Priority: Major  (was: Trivial)

> Make pyspark interface friendly with mypy 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: Major
>
> 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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