如何过滤数据帧中仅包含特定重复字符的元素

import pandas as pd

def filter_dataframe(dataframe, target_character):
    filtered_dataframe = dataframe.copy()
    for index, row in filtered_dataframe.iterrows():
        element = row['column_name']  # 替换为实际的列名
        if is_only_repeating_character(element, target_character):
            filtered_dataframe.drop(index, inplace=True)
    return filtered_dataframe

def is_only_repeating_character(element, target_character):
    # 判断元素是否仅包含特定重复字符
    return len(set(element)) == 1 and element[0] == target_character

# 示例用法
data = {'column_name': ['AAAA', 'ABAB', 'CCCC', 'DDDD']}
df = pd.DataFrame(data)
filtered_df = filter_dataframe(df, 'A')
print(filtered_df)