BUG: setting column with 2D object array raises #61026
Description
Research
-
I have searched the [pandas] tag on StackOverflow for similar questions.
-
I have asked my usage related question on StackOverflow.
Link to question on StackOverflow
Question about pandas
I found that setting pandas DataFrame column with a 2D numpy array whose dtype is object will cause a wierd error. I wonder why it happens.
The code I ran is as follows:
import numpy as np import pandas as pd print(f"numpy version: {np.__version__}") print(f"pandas version: {pd.__version__}") data = pd.DataFrame({ "c1": [1, 2, 3, 4, 5], }) t1 = np.array([["A"], ["B"], ["C"], ["D"], ["E"]]) data["c1"] = t1 # This works well t2 = np.array([["A"], ["B"], ["C"], ["D"], ["E"]], dtype=object) data["c1"] = t2 # This throws an error Result (some unrelated path removed):
numpy version: 2.2.3 pandas version: 2.2.3 Traceback (most recent call last): File "...\test.py", line 15, in <module> data["c1"] = t2 # This throws an error ~~~~^^^^^^ File "...\Anaconda\envs\test\Lib\site-packages\pandas\core\frame.py", line 4311, in __setitem__ self._set_item(key, value) ~~~~~~~~~~~~~~^^^^^^^^^^^^ File "...\Anaconda\envs\test\Lib\site-packages\pandas\core\frame.py", line 4524, in _set_item value, refs = self._sanitize_column(value) ~~~~~~~~~~~~~~~~~~~~~^^^^^^^ File "...\Anaconda\envs\test\Lib\site-packages\pandas\core\frame.py", line 5267, in _sanitize_column arr = sanitize_array(value, self.index, copy=True, allow_2d=True) File "...\Anaconda\envs\test\Lib\site-packages\pandas\core\construction.py", line 606, in sanitize_array subarr = maybe_infer_to_datetimelike(data) File "...\Anaconda\envs\test\Lib\site-packages\pandas\core\dtypes\cast.py", line 1181, in maybe_infer_to_datetimelike raise ValueError(value.ndim) # pragma: no cover ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ValueError: 2 I'm not sure whether it is the expected behaviour. I find it strange because simply adding dtype=object will cause the error.