1 """

     2     Iterate over lines in file-like objects (without buffering lines!), write (flushing output).

     3 """

     4 

     5 import logging; log = logging.getLogger('pvl.syslog.file')

     6 

     7 class File (object) :

     8     """

     9         Follow a file-like object, reading lines until no more are available. Never raises EOFError.

    10 

    11         Works with python file objects that buffer readlines() when using e.g. `tail -f ... | python -u ...`.

    12 

    13         readline() may block once there is no more input available, or may return None for evermore.

    14 

    15         There is no fileno(), this is not pollable. At all. Don't even iterate on this with a timeout.

    16         XXX: should this really return None? Might really be better to raise EOFError.. except that readlines() should return normally at EOF...

    17     """

    18 

    19     @classmethod

    20     def open (cls, path, mode='r', **opts) :

    21         return cls(open(path, mode), **opts)

    22 

    23     EOL = '\n'

    24 

    25     def __init__ (self, file) :

    26         log.debug("%s", file)

    27 

    28         self.file = file

    29         

    30     def readline (self) :

    31         """

    32             Reads a line from the file, without trailing \n.

    33 

    34             Returns None on EOF.

    35         """

    36 

    37         line = self.file.readline()

    38 

    39         if not line :

    40             line = None

    41         else : 

    42             line = line.rstrip('\r\n')

    43 

    44         log.debug("%s", line)

    45 

    46         return line

    47 

    48     def readlines (self) :

    49         """

    50             Reads any available lines from the file.

    51         """

    52 

    53         while True :

    54             line = self.readline()

    55             

    56             if line is None :

    57                 return

    58             else :

    59                 yield line

    60 

    61     __iter__ = readlines

    62 

    63     def writeline (self, line, eol=EOL) :

    64         """

    65             Write out line, flushing.

    66         """

    67 

    68         self.file.write(line)

    69         self.file.write(eol)

    70         self.file.flush()

    71 

    72     __call__ = writeline

    73