[Python] Can't get grouped data into numpy array

I have a CSV file like this:

Ngày(Date),Số(Number)
07/03/2025,8
07/03/2025,9
...
06/03/2025,6
06/03/2025,10
06/03/2025,18
06/03/2025,14
...


(Each day has 27 numbers)

I want to predict a list of 27 numbers on the next day using LSTM. It keeps getting an error on this step:

data_matrix = np.array(grouped_data.loc[:, "Số"].tolist())


with

KeyError: 'Số'


(which means 'Number')

Here is my code:

import numpy as np
import pandas as pd

df = pd.read_csv("C:/Users/Admin/lonum_fixed.csv", encoding="utf-8", sep=",")
df.columns = df.columns.str.strip()

grouped_data = df.groupby("Ngày")[["Số"]].apply(lambda x: list(map(int, x["Số"].values))).reset_index()
grouped_data["Số"] = grouped_data["Số"].apply(lambda x: eval(x) if isinstance(x, str) else x)

data_matrix = np.array(grouped_data.loc[:, "Số"].tolist())

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