Class LogWriter

INPUTS:
  stream -- stream -- output stream to use, must support write, flush, close
         -- str -- filename to use (.gz added automatically if not present)
         -- None -- logger started in uninitialized state; use open()
  sync -- boolean -- set to force a flush after every log entry.

ATTRIBUTES:
  .s -- the open stream
  .sync -- auto-flush flag
  .timeUnit -- time unit for log timestamps; default is millisecond

Overrides: object.__init__

Open a logging stream. 
INPUT:
  stream -- str -- a file name for the log. A .gz will be appended if not
            present. Log will be stored as a gzip YAML file.
         -- file-like -- an object with .write() .flush() and .close() 
            methods. Log will be sent as YAML text, with a single .write()
            for each entry of the log.

Write a log entry. Each entry consists of a topic string and an automatically generated timestamp, and may include a dictionary of additional attributes supplied as keyword arguments.

The log entry will be emitted as a YAML document (entry starting with ---) that contains a mapping with keys TIME for the timestamp (in units of .timeUnit) and TOPIC for the topic.

If .sync is set, the stream will be flushed after each entry.

Wrap the specified callable and log results of calls.
INPUTS:
  fun -- callable -- "getter" function with no params
  fmt -- callable -- formatting function for the parameter. 
            Must return something yaml can safe_dump()
  attr -- dict -- dictionary of extra attributes for log entry 
OUTPUTS:
  callable function that calls fun() and logs the results   
  
Typical usage is to take an existing getter function and replace it in 
in place with the wrapped getter:
>>> def dummyGetter():
>>>   return int(raw_input())
>>> L = joy.loggit.LogWriter("foo")
>>> g = L.getterWrapperFor(dummyGetter
    ,fmt=lambda x : "0x%X" % x
    , attr=dict(sparrow = 'african'))
>>> g()
258
258
>>> L.close()
>>> !gunzip -c foo.gz
--- {TIME: ????, TOPIC: getter, func_name: dummyGetter, sparrow: african, value: '0x102'}

Wrap the specified callable and log parameters of calls.
INPUTS:
  fun -- callable function with one parameter
  name -- function name to use in 
  ifmt -- formatting function for arguments
  ofmt -- formatting function for results / None to omit result
OUTPUTS:
  callable function that logs the parameter and then
  calls fun() with it and logs the results    

Usage -- see example for getterWrapperFor