Using Data Classes in Python (Summary)

Nice class! (pun intended) Can you put a pandas dataframe in a data class? Would you want to?

Hi Jon,

for your first question I guess there are two answers. You can definitely define a data class where one of the fields is a pandas dataframe, for instance to keep some related information together with it:

from dataclasses import dataclass
import pandas as pd

@dataclass
class DataRecord:
    data: pd.DataFrame
    owner: str
    origin: str

things = DataRecord(
    pd.read_csv("things.csv"),
    owner="gahjelle",
    origin="things.csv"
)

Depending on your use case, something like this could be a good idea although it would have a couple of drawbacks as well:

• You’d need to reach into .data to access dataframe methods, for instance things.data.query("value > 0")
• All dataframe methods would still return a dataframe and not a DataRecord, so you would have to manually move the extra information around:

positive_things = DataRecord(
    things.data.query("value > 0"),
    owner=things.owner,
    origin=things.origin,
)

pandas dataframes have a .attrs which may be a better option for storing these kinds of metadata.

Another way to put a pandas dataframe into a data class would be to extract the information of the dataframe and put it into a data class with one field for each column in the dataframe.

You can then either manually specify the fields of the dataframe or get them from your dataframe directly:

import pandas as pd
from dataclasses import make_dataclass

things = pd.read_csv("things.csv")
Things = make_dataclass("Things", things.columns)

things_dc = Things(**things.to_dict(orient="list"))

The things_dc will now contain all the information in the data frame (except the index). However, you’ve lost all the pandas methods, so it’s much less usable for doing any kind of analysis.

So to sum up, you can put a pandas dataframe into a data class, but I don’t think there are any general benefits in doing so. You may find a special usecase where it could be convenient though.

Thanks for introducing bpython, the enhanced repl is way better!

Really nice tutorial, thank you!

I wish we can spend more time on __slots__ or I wish there is a separate, advanced tutorial.