Python中的open(filename,'w')中的w代表什么意思

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open(filename,‘w’)中的w代表什么意思

The argument mode points to a string beginning with one of the following
sequences (Additional characters may follow these sequences.):

• ``r’’ ------ Open text file for reading. The stream is positioned at the
  beginning of the file.

• ``r+’’ ------ Open for reading and writing. The stream is positioned at the
  beginning of the file.

• ``w’’ ------Truncate file to zero length or create text file for writing.
  The stream is positioned at the beginning of the file.

• ``w+’’ ------Open for reading and writing. The file is created if it does not
  exist, otherwise it is truncated. The stream is positioned at
  the beginning of the file.

• ``a’’ ------Open for writing. The file is created if it does not exist. The
  stream is positioned at the end of the file. Subsequent writes
  to the file will always end up at the then current end of file,
  irrespective of any intervening fseek(3) or similar.

• ``a+’’ ------Open for reading and writing. The file is created if it does not
  exist. The stream is positioned at the end of the file. Subse-
  quent writes to the file will always end up at the then current
  end of file, irrespective of any intervening fseek(3) or similar.

seek() 方法用于移动文件读取指针到指定位置。

readline() 方法用于从文件读取整行，包括 “\n” 字符。如果指定了一个非负数的参数，则返回指定大小的字节数，包括 “\n” 字符。