Skip call to .tolist() when creating pd.Index#10619
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dcherian merged 1 commit intopydata:mainfrom Aug 13, 2025
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`np.tile` returns an NDArray and there is no need to convert this to a Python `list` prior to passing it to `pd.MultiIndex`. The interface to Pandas requires the object to be array-like, and one of the first things that the constructor does is coerce the list back to an NDArray. For arrays with large coordinate axes, `to_dataframe()` is extremely slow due to Pandas needing to iterate through a `list` object rather than an array. For an (1000, 500, 20) array -- 10M rows in the cartesian product -- this results in a ~20x speed-up for `xr.Dataset.to_dataframe()` (tested on x86 and Apple Silicon). ```python da = xr.DataArray(np.ones((1000, 500, 20)), name="foo") da.to_dataframe() ``` Closes pydata#10617
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np.tilereturns an NDArray and there is no need to convert this to a Pythonlistprior to passing it topd.MultiIndex. The interface to Pandas requires the object to be array-like, and one of the first things that the constructor does is coerce the list back to an NDArray.For arrays with large coordinate axes,
to_dataframe()is extremely slow due to Pandas needing to iterate through alistobject rather than an array.For an (1000, 500, 20) array -- 10M rows in the cartesian product -- this results in a ~20x speed-up for
xr.Dataset.to_dataframe()(tested on x86 and Apple Silicon).tolist()when constructing pandas MultiIndex? #10617