Python Pandas:如何删除列中的异常值，并将其替换为先前的值(假设它们不是异常值)？

import pandas as pd
import numpy as np

data = {'A': [1, 2, 3, np.nan, 5, 6, 7, 8, 9, 10]}
df = pd.DataFrame(data)

df['A'] = df['A'].fillna(method='ffill')

threshold = 3
mean = df['A'].mean()
std = df['A'].std()
df['A'] = np.where((df['A'] > mean + threshold * std) | (df['A'] < mean - threshold * std), df['A'].shift(1), df['A'])

import pandas as pd
import numpy as np

data = {'A': [1, 2, 3, np.nan, 5, 6, 7, 8, 9, 10]}
df = pd.DataFrame(data)

df['A'] = df['A'].fillna(method='ffill')

threshold = 3
mean = df['A'].mean()
std = df['A'].std()
df['A'] = np.where((df['A'] > mean + threshold * std) | (df['A'] < mean - threshold * std), df['A'].shift(1), df['A'])

print(df)