[ 
https://issues.apache.org/jira/browse/ARROW-2136?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
 ]

Matthew Gilbert updated ARROW-2136:
-----------------------------------
    Description: 
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}

  was:
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:python}
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}


> Non nullable schema ignored
> ---------------------------
>
>                 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
>            Priority: Major
>
> 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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