Single and multiple line status updates with minimal update sequences.

Latest release 20220530:

• UpdProxy: new .suffix property.
• Upd: new run_task context manager to display an UpdProxy while something runs, with optional ticker.
• Small bugfix.

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 demo()

A tiny demo function for visual checking of the basic functionality.

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 pfxprint(*a, **kw)

Wrapper for cs.pfx.pfxprint to pass print_func=cs.upd.print.

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

from cs.upd import pfxprint

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.__init__(self, backend=None, columns=None, disabled=None): Initialise the Upd.

Parameters:

• backend: the output file, default sys.stderr
• columns: the width of the output, default from the width of the backend tty if it is a tty, 80 otherwise
• disabled: if true, disable the output - just keep state; default true if the output is not a tty; this automatically silences the Upd if stderr is not a tty

Function upd_proxy(*da, **dkw)

Decorator to create a new UpdProxy and record it as state.proxy.

Parameters:

• func: the function to decorate
• prefix: initial proxy prefix, default func.__name__
• insert_at: the position for the new proxy, default 1

Typical example:

from cs.upd import upd_proxy, state as upd_state
...
@upd_proxy
def func*(self, ...):
    proxy = upd_state.proxy
    proxy.prefix = str(self) + " taskname"

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, prefix=None, suffix=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 for the new status line

Release Log

Release 20220530:

• UpdProxy: new .suffix property.
• Upd: new run_task context manager to display an UpdProxy while something runs, with optional ticker.
• Small bugfix.

Release 20220504:

• Upd.above: do a disable/enable around the yield, use try/finally for reliability.
• Upd.delete: just warn about index out of range, seems it can happen during interpreter shutdown; to be debugged later.

Release 20220429:

• UpdProxy: accept optional prefix= parameter.
• New pfxprint wrapper for cs.pfx.pfxprint, like the print wrapper.

Release 20210717: Docstring update.

Release 20210507: Upgrade dependency on cs.context for StackableState.

Release 20210428.4: Another dummy release during debugging.

Release 20210428.3: Repeat the previous release, again again.

Release 20210428.2: Repeat the previous release, again.

Release 20210428.1: Repeat the previous release.

Release 20210428: Do curses.setupterm() during iinit, avoid failure when stdout is not a tty.

Release 20210316:

• New UpdProxy.extend_prefix context manager to extend the proxy prefix around a suite.
• New global "state" StackableStatei object with an automatic .upd attribute.
• New @upd_proxy decorator to create an UpdProxy for the duration of a function call and record it as state.proxy.
• Bugfix Upd.insert: add slots.insert and proxies.insert missing from the no-display path.
• Rename private method Upd._adjust_text_v to public method Upd.diff.

Release 20210122:

• Autocreate slot 0 on first use.
• Reliable cleanup at exit.
• Fix a display small display issue.

Release 20201202:

• Fix for batch mode - handle failure of curses.setupterm(), throws TypeError.
• Upd.insert: defer check for cuu1 capability until there's at least one line already.

Release 20201102:

• Upd.nl: simple approach when there are no status lines.
• Upd: new cursor_visible and cursor_invisible methods to show and hide the cursor.

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.