如何在dataframe中创建缺少的列并按正确的顺序放置它

import pandas as pd
import numpy as np

columns = ['col1', 'col2', 'col3']  # 列的顺序
df = pd.DataFrame(columns=columns)  # 创建空的dataframe

missing_columns = [col for col in columns if col not in df.columns]

for col in missing_columns:
    df[col] = np.nan
df = df[columns]  # 按正确的顺序放置列

import pandas as pd
import numpy as np

# 创建空的dataframe并指定列的顺序
columns = ['col1', 'col2', 'col3']
df = pd.DataFrame(columns=columns)

# 检查dataframe中是否存在指定的列
missing_columns = [col for col in columns if col not in df.columns]

# 创建缺少的列并按正确的顺序放置
for col in missing_columns:
    df[col] = np.nan
df = df[columns]  # 按正确的顺序放置列

print(df)