cs.x 20181231

X(), for low level debugging

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_discard, X_logger and 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 if X_discard then discard the message; otherwise write the message to sys.stderr. X_discard's default value is not sys.stderr.isatty().

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

Unconditionally write the message msg.

If there are positional arguments after msg, format msg using %-expansion with those arguments.

Keyword arguments:

• file: optional keyword argument specifying the output file.
• colour: optional text colour. If specified, surround the message with ANSI escape sequences to render the text in that colour.

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 if X_discard then discard the message; otherwise write the message to sys.stderr.