pandas--fillna将nan替换

如下创建一个dataframe，其中age有一行为空

import pandas as pd
from numpy import NaN

df = pd.DataFrame({'age': [11, NaN, 22], 'sex': ['man', 'woman', 'man']})
print(df)
>>>     age    sex
	0  11.0    man
	1   NaN  woman
	2  22.0    man

用fillna函数替换nan值，例如替换为-1

df['age'] = df['age'].fillna(-1)
print(df)
>>>     age    sex
	0  11.0    man
	1  -1.0  woman
	2  22.0    man