For循环在csv文件中两次插入相同的数据

Question

出于某种原因，我用于检查修改后的文件的for循环两次插入相同的文件数据。我希望将文件数据一次插入到csv文件中。我正在使用熊猫将数据插入到csv文件中。如何解决此错误？

问题代码：

 try:
        PARENT_DIR = os.path.abspath('.')
        assert os.path.basename(PARENT_DIR) == 'Projects_Website'
    except AssertionError:
        in_dir = False
        while not in_dir:
            os.chdir('..')
            PARENT_DIR = os.path.abspath('.')
            try:
                assert os.path.basename(PARENT_DIR) == 'Projects_Website'
                in_dir = True
                break
            except AssertionError:
                continue
    _history = ModHistory.history(os.path.abspath('./src/mod_history'))
    os.chdir('../..')
    PARENT_DIR = os.path.abspath('.')
    for file in os.listdir(PARENT_DIR):
        if file in MOD_FILES:
            continue
        else:
            modTime = os.path.getmtime(file)
            current = datetime.datetime.fromtimestamp(modTime).strftime('%Y-%d-%m %H:%M:%S')
            history = _history
            for file_name, timestamp in history.items():
                if current == timestamp and file == file_name:
                    continue
                else:
                    if current != timestamp and file == file_name:
                        MOD_FILES.append(file)
                        # Code for updating csv file here
                    elif file != file_name:
                        if file in FOLDERS:
                            continue
                        else:
                            history_manager = ModHistory(file, current)
                            history_manager.insert_history()
                            os.chdir('../..')

ModHistory：__init__和insert_history（）源：

__init__：

def __init__(self, filename, timestamp):
        current_path = os.path.abspath('.')
        try:
            assert os.path.basename(current_path) == 'mod_history'
        except AssertionError:
            if os.path.basename(current_path) == 'Projects_Website':
                os.chdir('./src/mod_history')
            elif os.path.basename(current_path) == 'src':
                os.chdir('./mod_history')

        del current_path
        self.file = filename
        self.timestamp = timestamp

insert_history（）：

def insert_history(self):
        """
        Inserts file history data to csv file
        """
        print(self.file)
        print(self.timestamp)
        df = pd.DataFrame({"filename": [self.file], "timestamp": [self.timestamp]}, dtype='category')
        df.to_csv("modifications.csv", encoding="utf-8", mode='a', header=False)

Csv文件：

0,__init__.py,2020-10-26 19:01:10
0,_mod_history.py,2020-31-10 09:58:00
0,modifications.csv,2020-31-10 10:13:16
0,.gitignore,2020-24-10 11:23:50
0,README.md,2020-22-10 17:38:07
0,README.md,2020-22-10 17:38:07
0,requirements.txt,2020-31-10 10:34:37
0,requirements.txt,2020-31-10 10:34:37