如何使用pandas将行从一个数据帧逐个添加到另一个数据帧

import pandas as pd

source_df = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]})
target_df = pd.DataFrame()

for index, row in source_df.iterrows():
    target_df = target_df.append(row)

target_df = target_df.reset_index(drop=True)

import pandas as pd

source_df = pd.DataFrame({'A': [1, 2, 3], 'B': [4, 5, 6]})
target_df = pd.DataFrame()

for index, row in source_df.iterrows():
    target_df = target_df.append(row)

target_df = target_df.reset_index(drop=True)