BUG: Copying an empty DataFrame with index results in a broken BlockManager · Issue #5932 · pandas-dev/pandas (original) (raw)

The following line illustrates the problem:

df = pd.DataFrame(index=[0]).copy()
df["a"] = 0

This results in an AttributeError since the function BlockManager.make_empty initialises df._data.blocks with a numpy array object instead of an empty list. Thus subsequent calls to blocks.pop and blocks.append fail.

I have a patch coming up.