Why Python does not see all the rows in a file?

You most likely have a file with one or more DOS EOF (CTRL-Z) characters in it, ASCII codepoint 0x1A. When Windows opens a file in text mode, it'll still honour the old DOS semantics and end a file whenever it reads that character. See Line reading chokes on 0x1A.

Only by opening a file in binary mode can you bypass this behaviour. To do so and still count lines, you have two options:

• read in chunks, then count the number of line separators in each chunk:

  def bufcount(filename, linesep=os.linesep, buf_size=2 ** 15):    lines = 0    with open(filename, 'rb') as f:        last = ''        for buf in iter(f.read, ''):            lines += buf.count(linesep)            if last and last + buf[0] == linesep:                # count line separators straddling a boundary                lines += 1            if len(linesep) > 1:                last = buf[-1]    return lines

  Take into account that on Windows os.linesep is set to \r\n, adjust as needed for your file; in binary mode line separators are not translated to \n.

• Use io.open(); the io set of file objects open the file in binary mode always, then do the translations themselves:

  import iowith io.open(filename) as f:    lines = sum(1 for line in f)