lsst.log.utils.LogRedirect Class Reference

Public Member Functions
	__init__ (self, fd=1, dest=sys.stderr, encoding="utf-8", errors="strict")
	finish (self)

Protected Attributes
	_fd
	_dest
	_filehandle
	_thread

Detailed Description

Redirect a logging file descriptor to a Python stream.

Parameters
----------
fd : `int`
    File descriptor number, usually 1 for standard out, the default log
    output location.
dest : `io.TextIOBase`
    Destination text stream, often `sys.stderr` for ipython or Jupyter
    notebooks.
encoding : `str`
    Text encoding of the data written to fd.
errors : `str`
    Encoding error handling.

Notes
-----
Inspired by `this Stack Overflow answer
<https://stackoverflow.com/questions/41216215>`_

Definition at line 77 of file utils.py.

Constructor & Destructor Documentation

__init__()

lsst.log.utils.LogRedirect.__init__	(		self,
			fd = 1,
			dest = sys.stderr,
			encoding = "utf-8",
			errors = "strict" )

Definition at line 99 of file utils.py.

    def __init__(self, fd=1, dest=sys.stderr, encoding="utf-8", errors="strict"):
        self._fd = fd
        self._dest = dest
        # Save original filehandle so we can restore it later.
        self._filehandle = os.dup(fd)
 
        # Redirect `fd` to the write end of the pipe.
        pipe_read, pipe_write = os.pipe()
        os.dup2(pipe_write, fd)
        os.close(pipe_write)
 
        # This thread reads from the read end of the pipe.
        def consumer_thread(f, data):
            while True:
                buf = os.read(f, 1024)
                if not buf:
                    break
                data.write(buf.decode(encoding, errors))
            os.close(f)
            return
 
        # Spawn consumer thread with the desired destination stream.
        self._thread = threading.Thread(target=consumer_thread, args=(pipe_read, dest))
        self._thread.start()
 

Member Function Documentation

finish()

lsst.log.utils.LogRedirect.finish

(

self

)

Stop redirecting output.

Definition at line 124 of file utils.py.

    def finish(self):
        """Stop redirecting output.
        """
 
        # Cleanup: flush streams, restore `fd`
        self._dest.flush()
        # This dup2 closes the saved file descriptor, which is now the write
        # end of the pipe, causing the thread's read to terminate
        os.dup2(self._filehandle, self._fd)
        os.close(self._filehandle)
        self._thread.join()
 
 

Member Data Documentation

_dest

lsst.log.utils.LogRedirect._dest

protected

Definition at line 101 of file utils.py.

_fd

lsst.log.utils.LogRedirect._fd

protected

Definition at line 100 of file utils.py.

_filehandle

lsst.log.utils.LogRedirect._filehandle

protected

Definition at line 103 of file utils.py.

_thread

lsst.log.utils.LogRedirect._thread

protected

Definition at line 121 of file utils.py.

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The documentation for this class was generated from the following file:

• /j/snowflake/release/lsstsw/stack/lsst-scipipe-8.0.0/Linux64/log/g2079a07aa2+86d27d4dc4/python/lsst/log/utils.py