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https://issues.apache.org/jira/browse/ARROW-6222?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16906196#comment-16906196
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Joris Van den Bossche commented on ARROW-6222:
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> Is there currently any way to serialize a dataframe that contains vectors
> (1d tensors) with feather?
I don't think so. At least not at the moment, as feather does not support a
list type. But see ARROW-5510 for future plans to at some point be updated to
the arrow IPC format (which will then support list types).
At the moment, I think parquet is the better alternative if you want (simple,
non-nested) list support in file format supported by Arrow.
> Serialising numpy array yields `pyarrow.lib.ArrowNotImplementedError:
> list<item: float>`
> ----------------------------------------------------------------------------------------
>
> Key: ARROW-6222
> URL: https://issues.apache.org/jira/browse/ARROW-6222
> Project: Apache Arrow
> Issue Type: Bug
> Affects Versions: 0.14.1
> Reporter: Marcel Ackermann
> Priority: Major
>
> I want to serialize pytorch tensors, but as they are not implemented in arrow
> yet I convert them to a numpy array like this: {{t.numpy()}}
> ([https://pytorch.org/docs/stable/tensors.html?highlight=numpy#torch.Tensor.numpy)]
> which returns an {{ndarray{{. My tensors are 1-dimensional, the result is a
> 1-dimensional ndarray.
> Calling {{df.to_feather("fname.feather")}} yields
> {{pyarrow.lib.ArrowNotImplementedError: list<item: float>}}.
> Next I tried {{pyarrow.array(t.numpy())}} which results in
> {{pyarrow.lib.ArrowInvalid: ('Could not convert [\n 0.00500498,\n
> -0.00732583,\n... with type pyarrow.lib.FloatArray: did not recognize Python
> value type when inferring an Arrow data type', 'Conversion failed for column
> 0 with type object')}}.
> I would appreciate if this would work more out-of-the-box.
> Upon request a full example:
> {code:python}
> import torch
> import pyarrow
> import pandas as pd
> pd.DataFrame([[torch.ones(2)]], columns=["0"]).to_feather("fname.feather")
> pd.DataFrame([[torch.ones(2).numpy()]],
> columns=["0"]).to_feather("fname.feather")
> pd.DataFrame([[pyarrow.array(torch.ones(2).numpy())]],
> columns=["0"]).to_feather("fname.feather")
> {code}
> {code:python}
> ArrowInvalid: ('Could not convert tensor([1., 1.]) with type Tensor: did not
> recognize Python value type when inferring an Arrow data type', 'Conversion
> failed for column 0 with type object')
> ArrowNotImplementedError: list<item: float>
> ArrowInvalid: ('Could not convert [\n 1,\n 1\n] with type
> pyarrow.lib.FloatArray: did not recognize Python value type when inferring an
> Arrow data type', 'Conversion failed for column 0 with type object')
> {code}
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