Pandas - Different Dtype Column Before/after Reading A File

I'm referring to this question since I'm facing with a weird behaviour of column types before and after reading the same dataframe from a .csv. Starting from: In [137]: df Out[137]

Solution 1:

You might want to use pickle IO:

import pandas as pd
df = pd.DataFrame({'a': [['a', 'b']]})
df.a.dtype
df.to_pickle('stuff.pkl.bin')
>>> pd.read_pickle('stuff.pkl.bin').a
0    [a, b]
Name: a, dtype: object

CSV is a very limited, textual, format. Conversely, pickle (and its variants) are binary object formats.