In [21]: df = DataFrame(dict(A = 'foo', B = 'bar'),index=range(5)).set_index("A") In [22]: df.to_hdf('store.h5', 'test', format='table', min_itemsize={'index': 10}) In [23]: store = pd.HDFStore('store.h5') In [24]: store.get_storer('test').table Out[24]: /test/table (Table(5,)) '' description := { "index": StringCol(itemsize=3, shape=(), dflt=b'', pos=0), "values_block_0": StringCol(itemsize=3, shape=(1,), dflt=b'', pos=1)} # <---- I think this should be 10 byteorder := 'irrelevant' chunkshape := (10922,) autoindex := True colindexes := { "index": Index(6, medium, shuffle, zlib(1)).is_csi=False}

In [25]: df.index.name = 'theindex' In [26]: df.to_hdf('store.h5', 'test2', format='table', min_itemsize={'theindex': 10}) --------------------------------------------------------------------------- ValueError Traceback (most recent call last)