[jira] [Commented] (ARROW-2136) [Python] Non-nullable schema fields not checked in conversions from pandas

["Joris Van den Bossche (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ARROW-2136?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16861474#comment-16861474 ] 

Joris Van den Bossche commented on ARROW-2136:
----------------------------------------------

I have a PR for ARROW-5169 (https://github.com/apache/arrow/pull/4397), which tries to use this nullability of the passed {{schema}}, but I should check how my PR interacts with passing data with nulls.

> [Python] Non-nullable schema fields not checked in conversions from pandas
> --------------------------------------------------------------------------
>
>                 Key: ARROW-2136
>                 URL: https://issues.apache.org/jira/browse/ARROW-2136
>             Project: Apache Arrow
>          Issue Type: Bug
>          Components: Python
>    Affects Versions: 0.8.0
>            Reporter: Matthew Gilbert
>            Assignee: Joris Van den Bossche
>            Priority: Major
>             Fix For: 0.14.0
>
>
> If you provide a schema with {{nullable=False}} but pass a {{DataFrame}} which in fact has nulls it appears the schema is ignored? I would expect an error here.
> {code}
> import pyarrow as pa
> import pandas as pd
> df = pd.DataFrame({"a":[1.2, 2.1, pd.np.NaN]})
> schema = pa.schema([pa.field("a", pa.float64(), nullable=False)])
> table = pa.Table.from_pandas(df, schema=schema)
> table[0]
> <pyarrow.lib.Column object at 0x7f213bf2fb70>
> chunk 0: <pyarrow.lib.DoubleArray object at 0x7f213bf20ea8>
> [
>   1.2,
>   2.1,
>   NA
> ]
> {code}



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