无法将由coma分隔的字符串写入/读取到文件中

# 将字符串写入文件
def write_to_file(string, filename):
    # 拆分字符串为列表
    data_list = string.split(",")
    
    # 打开文件并写入数据
    with open(filename, "a") as file:
        for item in data_list:
            file.write(item + "\n")

# 从文件中读取字符串
def read_from_file(filename):
    # 读取文件内容
    with open(filename, "r") as file:
        data = file.read()
    
    # 将内容转换为字符串
    string = ",".join(data.splitlines())
    
    return string

# 测试写入和读取文件
data = "apple,banana,orange"
filename = "data.txt"

write_to_file(data, filename)
result = read_from_file(filename)

print("写入的字符串：", data)
print("从文件中读取的字符串：", result)