每次向dataframe添加新行时更新列

import pandas as pd

# 创建空的dataframe
df = pd.DataFrame(columns=['列1', '列2', '列3'], dtype=int)

# 添加新行
new_row = {'列1': 1, '列2': 2, '列3': 3}
df = df.append(new_row, ignore_index=True)

# 更新新行的列值
df.at[0, '列1'] = 10
df.at[0, '列2'] = 20
df.at[0, '列3'] = 30

# 打印dataframe
print(df)

import pandas as pd

# 创建空的dataframe
df = pd.DataFrame(columns=['列1', '列2', '列3'], dtype=int)

# 添加新行
new_row = {'列1': 1, '列2': 2, '列3': 3}
df = df.append(new_row, ignore_index=True)

# 更新新行的列值
df.loc[0, '列1'] = 10
df.loc[0, '列2'] = 20
df.loc[0, '列3'] = 30

# 打印dataframe
print(df)