There are variables X_train, X_test, y_train, y_test created through sklearn train_test_split. They contain text data in string format. Convert them to float numbers.

import pandas as pd
import numpy as np

df = pd.DataFrame(np.random.randn(10, 2), columns=['Col1', 'Col2'])

X_train, X_test, y_train, y_test = train_test_split(
    df['Col1'],
    df['Col2'],
    random_state=1
)

def convert_to_float(x_train, x_test, y_train, y_test):
    return (
        x_train.astype(float),
        x_test.astype(float),
        y_train.astype(float),
        y_test.astype(float)
    )
    
convert_to_float(X_train, X_test, y_train, y_test)