cs.upd 20201026.1

Single and multiple line status updates with minimal update sequences.

Single and multiple line status updates with minimal update sequences.

Latest release 20201026.1: Bugfix Upd.nl: simple output if there are no status lines to accomodate.

This is available as an output mode in cs.logutils.

Single line example:

from cs.upd import Upd, nl, print
.....
with Upd() as U:
    for filename in filenames:
        U.out(filename)
        ... process filename ...
        U.nl('an informational line to stderr')
        print('a line to stdout')

Multiline multithread example:

from threading import Thread
from cs.upd import Upd, print
.....
def runner(filename, proxy):
    # initial status message
    proxy.text = "process %r" % filename
    ... at various points:
        # update the status message with current progress
        proxy.text = '%r: progress status here' % filename
    # completed, remove the status message
    proxy.close()
    # print completion message to stdout
    print("completed", filename)
.....
with Upd() as U:
    U.out("process files: %r", filenames)
    Ts = []
    for filename in filenames:
        proxy = U.insert(1) # allocate an additional status line
        T = Thread(
            "process "+filename,
            target=runner,
            args=(filename, proxy))
        Ts.append(T)
        T.start()
    for T in Ts:
        T.join()

A note about Upd and terminals

I routinely use an Upd() as a progress reporting tool for commands running on a terminal. This attaches to sys.stderr by default. However, it is usually not desirable to run an Upd display if the backend is not a tty/terminal. Therefore, an Upd has a "disabled" mode which performs no output; the default behaviour is that this mode activates if the backend is not a tty (as tested by backend.isatty()). The constructor has an optional parameter disabled to override this default behaviour.

Function cleanupAtExit()

Cleanup function called at programme exit to clear the status line.

Function nl(msg, *a, **kw)

Write msg to file (default sys.stdout), without interfering with the Upd instance. This is a thin shim for Upd.print.

Function out(msg, *a, **outkw)

Update the status line of the default Upd instance. Parameters are as for Upd.out().

Function print(*a, **kw)

Wrapper for the builtin print function to call it inside Upd.above() and enforce a flush.

The function supports an addition parameter beyond the builtin print:

• upd: the Upd instance to use, default Upd()

Programmes integrating cs.upd with use of the builtin print function should use this at import time:

from cs.upd import print

Class Upd(cs.obj.SingletonMixin)

A SingletonMixin subclass for maintaining a regularly updated status line.

The default backend is sys.stderr.

Method Upd.__exit__(self, exc_type, exc_val, _)

Tidy up on exiting the context.

If we are exiting because of an exception which is not a SystemExit with a code of None or 0 then we preserve the status lines one screen. Otherwise we clean up the status lines.

Method Upd.__len__(self)

The length of an Upd is the number of slots.

Method Upd.above(self, need_newline=False)

Move to the top line of the display, clear it, yield, redraw below.

This context manager is for use when interleaving another stream with the Upd display; if you just want to write lines above the display for the same backend use Upd.nl.

The usual situation for Upd.above is interleaving sys.stdout and sys.stderr, which are often attached to the same terminal.

Note that the caller's output should be flushed before exiting the suite so that the output is completed before the Upd resumes.

Example:

U = Upd()   # default sys.stderr Upd
......
with U.above():
    print('some message for stdout ...', flush=True)

Method Upd.close(self)

Close this Upd.

Method Upd.closed(self)

Test whether this Upd is closed.

Method Upd.delete(self, index)

Delete the status line at index.

Return the UpdProxy of the deleted status line.

Method Upd.disable(self)

Disable updates.

Property Upd.disabled

Whether this Upd is currently disabled.

Method Upd.enable(self)

Enable updates.

Method Upd.flush(self)

Flush the backend stream.

Method Upd.insert(self, index, txt='', proxy=None)

Insert a new status line at index.

Return the UpdProxy for the new status line.

Method Upd.nl(self, txt, *a, redraw=False)

Write txt to the backend followed by a newline.

Parameters:

• txt: the message to write.
• a: optional positional parameters; if not empty, txt is percent formatted against this list.
• redraw: if true (default False) use the "redraw" method.

This uses one of two methods:

• insert above: insert a line above the top status line and write the message there.
• redraw: clear the top slot, write txt and a newline, redraw all the slots below.

The latter method is used if redraw is true or if txt is wider than self.columns or if there is no "insert line" capability.

Method Upd.normalise(txt)

Normalise txt for display, currently implemented as: unctrl(txt.rstrip()).

Method Upd.out(self, txt, *a, slot=0, raw_text=False, redraw=False)

Update the status line at slot to txt. Return the previous status line content.

Parameters:

• txt: the status line text.
• a: optional positional parameters; if not empty, txt is percent formatted against this list.
• slot: which slot to update; default is 0, the bottom slot
• raw_text: if true (default False), do not normalise the text
• redraw: if true (default False), redraw the whole line instead of doing the minimal and less visually annoying incremental change

Method Upd.proxy(self, index)

Return the UpdProxy for index. Returns None if index if out of range.

Method Upd.selfcheck(self)

Sanity check the internal data structures.

Warning: this uses asserts.

Method Upd.ti_str(self, ti_name)

Fetch the terminfo capability string named ti_name. Return the string or None if not available.

Method Upd.without(self, temp_state='', slot=0)

Context manager to clear the status line around a suite. Returns the status line text as it was outside the suite.

The temp_state parameter may be used to set the inner status line content if a value other than '' is desired.

Class UpdProxy

A proxy for a status line of a multiline Upd.

This provides a stable reference to a status line after it has been instantiated by Upd.insert.

The status line can be accessed and set via the .text property.

An UpdProxy is also a context manager which self deletes on exit:

U = Upd()
....
with U.insert(1, 'hello!') as proxy:
    .... set proxy.text as needed ...
# proxy now removed

Method UpdProxy.__init__(self, index=1, upd=None, text=None)

Initialise a new UpdProxy status line.

Parameters:

• index: optional position for the new proxy as for Upd.insert, default 1 (directly above the bottom status line)
• upd: the Upd instance with which to associate this proxy, default the default Upd instance (associated with sys.stderr)
• text: optional initial text fot the new status line

Method UpdProxy.__call__(self, msg, *a)

Calling the proxy sets its .text property in the form used by other messages: (msg,*a)

Method UpdProxy.__del__(self)

Delete this proxy from its parent Upd.

Method UpdProxy.delete(self)

Delete this proxy from its parent Upd.

Method UpdProxy.insert(self, index, txt='')

Insert a new UpdProxy at a position relative to this UpdProxy. Return the new proxy.

This supports the positioning of related status lines.

Property UpdProxy.prefix

The current prefix string.

Method UpdProxy.reset(self)

Clear the proxy: set both the prefix and text to ''.

Property UpdProxy.text

The text of this proxy's slot, without the prefix.

Property UpdProxy.width

The available space for text after self.prefix.

This is available width for uncropped text, intended to support presizing messages such as progress bars. Setting the text to something longer will crop the rightmost portion of the text which fits.

Release Log

Release 20201026.1: Bugfix Upd.nl: simple output if there are no status lines to accomodate.

Release 20201026: Bugfix Upd.insert: accept insert(1) when len(self)==0.

Release 20201025:

• Upd: new .disabled property to allow inspection of disabledness.
• Upd.insert: accept negative insert indices to position from the top of the list.
• Upd.nl: use clear-to-end-of-line at the end of the message if available.
• UpdProxy: turn .prefix into a property which causes a redraw when changed.
• Upd.proxy(index): return None if the index is out of range, accomodates racy or incorrect behaviour by a user.
• UpdProxy: cropped overflowing text gets a leading '<' to make it apparent.
• UpdProxy: new .insert() method to support insterting new proxies with respect to an existing proxy.
• UpdProxy: new reset() method, clears prefix and text.
• UpdProxy.init: BREAKING: make all arguments optional to aid use.
• Upd: do not make any slots unless required.
• Make the compute-redraw-strings methods private.

Release 20200914: Bugfix UpdProxy.enter: return self.

Release 20200716.1: DISTINFO: make the cs.obj requirement more specific due to the SingletonMixin API change.

Release 20200716: Update for changed cs.obj.SingletonMixin API.

Release 20200626.1: Upd.exit: bugfix test of SystemExit exceptions.

Release 20200626:

• UpdProxy: call self.delete on del.
• If self._backend is None act as if disabled, occurs during shutdown.
• Upd.delete: ignore attempts to delete the last line, also occurs during shutdown.

Release 20200621: New "disabled" mode, triggered by default if not backend.isatty().

Release 20200613:

• New UpdProxy.call which sets the .text property in the manner of logging calls, with (msg,*a).
• New Upd.normalise static method exposing the text normalisation unctrl(text.rstrip()).
• New UpdProxy.prefix attribute with a fixed prefix for status updates; prefix+text is left cropped for display purposes when updated.
• New UpdProxy.width property computing the space available after the prefix, useful for sizing things like progress bars.
• Make UpdProxy a context manager which self deletes on exit.
• Upd: make default backend=sys.stderr, eases the common case.
• New Upd.above() context manager to support interleaving another stream with the output, as when stdout (for print) is using the same terminal as stderr (for Upd).
• New out() top level function for convenience use with the default Upd().
• New nl() top level function for writing a line to stderr.
• New print() top level function wrapping the builtin print; callers can use "from cs.upd import print" to easily interleave print() with cs.upd use.

Release 20200517:

• Multiline support!
• Multiline support!
• Multiline support!
• New UpdProxy class to track a status line of a multiline Upd in the face of further inserts and deletes.
• Upd(...) now returns a context manager to clean up the display on its exit.
• Upd(...) is now a SingletonMixin in order to use the same state if set up in multiple places.

Release 20200229:

• Upd: can now be used as a context manager, clearing the line on exit.
• Upd.without is now a context manager, returning the older state, and accepting an optional inner state (default "").
• Upd is now a singleton factory, obsoleting upd_for.
• Upd.nl: use "insert line above" mode if supported.

Release 20181108: Documentation improvements.

Release 20170903:

• New function upd_for(stream) returning singleton Upds.
• Drop noStrip keyword argument/mode - always strip trailing whitespace.

Release 20160828:

• Use "install_requires" instead of "requires" in DISTINFO.
• Add Upd.flush method.
• Upd.out: fix longstanding trailing text erasure bug.
• Upd.nl,out: accept optional positional parameters, use with %-formatting if supplied, just like logging.

Release 20150118: metadata fix

Release 20150116: Initial PyPI release.