[jira] [Commented] (ARROW-5811) [Python] pyarrow.csv.read_csv: Ability to not infer column types.

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

    [ https://issues.apache.org/jira/browse/ARROW-5811?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16876025#comment-16876025 ] 

Antoine Pitrou commented on ARROW-5811:
---------------------------------------

No, {{convert_types}} must be the full mapping of column names to data types. C++ doesn't know about {{defaultdict}}...

We could add more inference options, though, for example to select the datatypes for which inference is enabled.

> [Python] pyarrow.csv.read_csv: Ability to not infer column types.
> -----------------------------------------------------------------
>
>                 Key: ARROW-5811
>                 URL: https://issues.apache.org/jira/browse/ARROW-5811
>             Project: Apache Arrow
>          Issue Type: Improvement
>          Components: Python
>    Affects Versions: 0.13.0
>         Environment: Ubuntu Xenial
>            Reporter: Bogdan Klichuk
>            Priority: Minor
>              Labels: csv, csvparser, pyarrow
>
> I'm trying to read CSV as is. All columns as strings. I don't know the schema of these CSVs and they will vary as they are provided by user.
> Right now i'm using pandas.read_csv(dtype=str) which works great, but since final destination of these CSVs are parquet files it seems like much more efficient to use pyarrow.csv.read_csv in future, as soon as this becomes available :)
> I tried things like `pyarrow.csv.read_csv(convert_types=ConvertOptions(columns_types=defaultdict(lambda: 'string')))` but it doesn't work.
> Maybe I just didnt' find something that already exists? :)



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