[jira] [Commented] (ARROW-5195) [Python] read_csv ignores null_values on string types

["Antoine Pitrou (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-5195?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16823789#comment-16823789 ] 

Antoine Pitrou commented on ARROW-5195:
---------------------------------------

Right, we should add an option for this. Currently any string is a valid string value.

> [Python] read_csv ignores null_values on string types
> -----------------------------------------------------
>
>                 Key: ARROW-5195
>                 URL: https://issues.apache.org/jira/browse/ARROW-5195
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: Python
>    Affects Versions: 0.13.0
>         Environment: Python 3.6, PyArrow 0.13.0, AWS linux, debian-slim in docker
>            Reporter: Scott Burns
>            Priority: Minor
>             Fix For: 0.14.0
>
>
> Let's write a simple CSV with NULL values in a string column:
> {quote}with open('foo.csv', 'w') as fobj:
>      fobj.write('col1,col2\n1,value\n2,NULL')
>  table = csv.read_csv('foo.csv')
>  table.column('col2').null_count # => 0
> {quote}
>  
>  table.column('col2').null_count will be 0, I think it should be 1. Passing in {{ConvertOptions(null_values=["NULL"])}} doesn't help.
>  
> Note that {{pandas.read_csv}} parses these NULLs correctly so I have a workaround available.
> But I'd prefer to natively read CSV from pyarrow if possible :)



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