问pandas to_numeric(…，downcast='float')失去精度

EN

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt

x, y = [], []
for idx, num in enumerate(range(1, 57, 2)):
    print(f"{idx+1}) Testing with {num} million records...")
    rows = num*(10**6)
    cols = ['col']

    df = pd.DataFrame(np.random.uniform(0, 9.761140e+02, size=(rows, len(cols))), columns=cols)
    df['col1'] = pd.to_numeric(df['col'], downcast='float')
    df['diff'] = df['col'] - df['col1']

    diff = df['col'].mean() - df['col1'].mean()

    x.append(num)
    y.append(diff)

plt.plot(x, y, 'ro')
plt.xlabel('number of rows (millions)')
plt.ylabel('precision value lost')
plt.show()