cs.x 20180726

X(), for low level debugging

X() is my function for low level ad hoc debug messages. It takes a message and optional format arguments for use with %. It is presented here in its own module for reuse.

It normally writes directly to sys.stderr but accepts an optional keyword argument file to specify a different filelike object. If file is not specified, its behaviour is further tweaked with the globals X_logger or X_via_tty: if X_logger then log a warning to that logger; otherwise, if X_via_tty then open /dev/tty and write the message to it; otherwise, write the message to sys.stderr.

Function X(msg, *args, **kw)

Unconditionally write the message msg.

• args: if not empty, format msg using %-expansion with args.
• file: optional keyword argument specifying the output file.

If file is not None, write to it unconditionally; otherwise, if X_logger then log a warning to that logger; otherwise, if X_via_tty then open /dev/tty and write the message to it; otherwise write the message to sys.stderr.