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