在For循环中替换Dataframe的所有列中的'-‘值

import pandas as pd
import numpy as np

# 创建示例DataFrame
df = pd.DataFrame({'A': [1, 2, '-', 4],
                   'B': [5, '-', 7, 8],
                   'C': ['-', 10, 11, 12]})

# 遍历DataFrame的所有列
for col in df.columns:
    # 将'-'替换为NaN
    df[col] = df[col].replace('-', np.nan)

# 输出替换后的DataFrame
print(df)

     A    B     C
0  1.0  5.0   NaN
1  2.0  NaN  10.0
2  NaN  7.0  11.0
3  4.0  8.0  12.0