tarfile.open每次覆蓋該文件

我正在嘗試創建python腳本來存檔和壓縮datewise tar文件中的一年前數據。腳本還生成存檔文件的日誌文件。我在linux上使用python 2.6。tarfile.open每次覆蓋該文件

這裏是我的代碼：

for search_date in dd_list: 
    tar_file = "/files/yearly_archive/nas_archive_" + search_date + ".tgz" 
    mytar = tarfile.open(tar_file,"w:gz") 
    log_file = "/files/yearly_archive/archive_log_" + search_date 
    fcount = 0 
    #print tar_file 
    #print log_file 
    f = open(log_file,'ab+') 
    for f_name, d_date in date_file_dict.iteritems(): 
     if d_date == search_date: 
      #print f_name 
      fcount += 1 
      mytar.add(f_name) 
      f.write(f_name + '\n') 
    date_occur_dict[search_date] = fcount 
    mytar.close() 
    f.close()

這裏登錄，如果它存在，但tar文件被覆蓋掉了每次當我運行該腳本文件得到追加。有沒有一種方法可以確保tar文件被附加，如果它存在，否則會被創建？

編輯：

我試圖爲ungzipping和添加添加代碼，但它無法正常工作。

for search_date in dd_list: 
    tar_file = "/files/yearly_archive/nas_archive_" + search_date + ".tgz" 
    zip = 1 
    try: 
     with open(tar_file,'ab+'): 
      import gzip 
      d_tar = gzip.open(tar_file,'wb') 
      zip = 0 
    except IOError: 
     print "Creating new tar file" 
    if zip == 1: 
     mytar = tarfile.open(tar_file,"w:gz") 
    else: 
     mytar = tarfile.open(d_tar,"w") 
    log_file = "/files/yearly_archive/archive_log_" + search_date 
    fcount = 0 
    #print tar_file 
    #print log_file 
    f = open(log_file,'ab+') 
    for f_name, d_date in date_file_dict.iteritems(): 
     if d_date == search_date: 
      #print f_name 
      fcount += 1 
      mytar.add(f_name) 
      f.write(f_name + '\n') 
    date_occur_dict[search_date] = fcount 
    mytar.close() 
    f.close()

我收到以下錯誤：

Traceback (most recent call last): 
    File "sort_archive.py", line 63, in <module> 
    mytar = tarfile.open(d_tar,"w") 
    File "/usr/lib64/python2.6/tarfile.py", line 1687, in open 
    return cls.taropen(name, mode, fileobj, **kwargs) 
    File "/usr/lib64/python2.6/tarfile.py", line 1697, in taropen 
    return cls(name, mode, fileobj, **kwargs) 
    File "/usr/lib64/python2.6/tarfile.py", line 1518, in __init__ 
    fileobj = bltn_open(name, self._mode) 
TypeError: coercing to Unicode: need string or buffer, instance found

來源

2013-10-08 user2501825