Package: cs.pfx
Dynamic message prefixes providing execution context.Latest release 20230604:
@pfx_method: handle methods with noname(generally a misuse of the decorator).The primary facility here isPfx,
a context manager which maintains a per thread stack of context prefixes.
There are also decorators for functions.
This stack is used to prefix logging messages and exception text with context.Usage is like this:from cs.logutils import setup_logging, info
from cs.pfx import Pfx
...
setup_logging()
...
def parser(filename):
  with Pfx(filename):
    with open(filename) as f:
      for lineno, line in enumerate(f, 1):
        with Pfx(lineno) as P:
          if line_is_invalid(line):
            raise ValueError("problem!")
          info("line = %r", line)This produces log messages like:datafile: 1: line = 'foo\n'and exception messages like:datafile: 17: problem!which lets one put just the relevant complaint in exception and log
messages and get useful calling context on the output.
This does make for wordier logs and exceptions
but used with a little discretion produces far more debuggable results.ClassPfxA context manager to maintain a per-thread stack of message prefixes.MethodPfx.__init__(self, mark, *args, **kwargs):
Initialise a new Pfx instance.Parameters:mark: message prefix stringargs: if not empty, apply to the prefix string with%absolute: optional keyword argument, defaultFalse. If
true, this message forms the base of the message prefixes;
earlier prefixes will be suppressed.loggers: which loggers should receive log messages.print: if true, print themarkon entry to thewithsuite.
This may be abool, implyingprint()ifTrue,
a callable which works likeprint(),
or a file-like object which implies usingprint(...,file=print).Note:
themarkandargsare only combined if thePfxinstance gets used,
for example for logging or to annotate an exception.
Otherwise, they are not combined.
Therefore the values interpolated are as they are when thePfxis used,
not necessarily as they were when thePfxwas created.
If theargsare subject to change and you require the original values,
apply them tomarkimmediately, for example:with Pfx('message %s ...' % (arg1, arg2, ...)):This is a bit more expensive as it incurs the formatting cost
whenever you enter thewithclause.
The common usage is:with Pfx('message %s ...', arg1, arg2, ...):Functionpfx(*da, **dkw)General purpose @pfx for generators, methods etc.Parameters:func: the function or generator function to decoratemessage: optional prefix to use instead of the function namemessage_args: optional arguments to embed in the preifx using%Example usage:@pfx
def f(....):
    ....Functionpfx_call(func, *a, **kw)Callfunc(*a,**kw)within an enclosingPfxcontext manager
reciting the function name and arguments.Example:>>> import os
>>> pfx_call(os.rename, "oldname", "newname")Functionpfx_iter(tag, iterable)Wrapper for iterables to prefix exceptions withtag.Functionpfx_method(*da, **dkw)Decorator to provide aPfxcontext for an instance method prefixingclassname.methodname.Ifuse_stris true (defaultFalse)
usestr(self)instead ofclassname.Ifwith_argsis true (defaultFalse)
include the specified arguments in thePfxcontext.
Ifwith_argsisTrue, this includes all the arguments.
Otherwisewith_argsshould be a sequence of argument references:
anintspecifies one of the positional arguments
and a string specifies one of the keyword arguments.Examples:class O:
    # just use "O.foo"
    @pfx_method
    def foo(self, .....):
        ....
    # use the value of self instead of the class name
    @pfx_method(use_str=True)
    def foo2(self, .....):
        ....
    # include all the arguments
    @pfx_method(with_args=True)
    def foo3(self, a, b, c, *, x=1, y):
        ....
    # include the "b", "c" and "x" arguments
    @pfx_method(with_args=[1,2,'x'])
    def foo3(self, a, b, c, *, x=1, y):
        ....ClassPfxCallInfo(Pfx)Subclass of Pfx to insert current function and caller into messages.Functionpfxprint(*a, print_func=None, **kw)Callprint()with the current prefix.The optional keyword parameterprint_funcprovides an alternative function to the builtinprint().FunctionPfxThread(target, **kw)Factory function returning aThreadwhich presents the current prefix as context.Functionprefix()Return the current Pfx prefix.FunctionPrePfx(tag, *args)Push a temporary value for Pfx._state._ur_prefix to enloundenify messages.Functionunpfx(s, sep=None)Strip the leading prefix from the stringsusing the prefix delimitersep(default fromDEFAULT_SEPARATOR:': ').This is a simple hack to support reporting error messages
which have had a prefix applied,
and fails accordingly if the base message itself contains the separator.FunctionXP(msg, *args, **kwargs)Variation oncs.x.Xwhich prefixes the message with the current Pfx prefix.FunctionXX(prepfx, msg, *args, **kwargs)Trite wrapper forXP()to transiently insert a leading prefix string.Example:XX("NOTE!", "some message")Release LogRelease 20230604:
@pfx_method: handle methods with noname(generally a misuse of the decorator).Release 20230331:
PfxThread: use HasThreadState.Thread, make target mandatory.Release 20221118:
pkg_tags: cs.py.func: update PyPI release: set pypi.release='20221118' [IGNORE]Release 20220918:Drop _PfxThreadState.raise_needs_prefix, supplant with more reliable special exception attribute.Pfx.exit: include more detail in (suppressed) "message not prefixed" message.Pfx.exit: more elaborate logic for exc_value.args.Release 20220523:
Pfx.umask: promote self.mark directly to ustr.Release 20220429:New Pfx.scope() context manager and Pfx.push(msg,*a) nonindenting Pfx push.pfxprint: new optional print_func keyword parameter.Release 20220227:Pfx.prefixify: change OSError.args action: prefixify the first string.XP: use DEFAULT_SEPARATOR on both paths.Release 20211031:
Pfx.prefixify_exception: skip attributes which are None.Release 20210913:
Pfx: do not fiddle with LookupError.args[0], it is the key.Release 20210906:New pfxprint which calls print() with the current prefix.Pfx.prefixify_exception: catch unexpected OSError.args value and report.@pfx: use pfx_call if there is no presupplied message argument.Release 20210801:
Bugfix for @pfx.Release 20210731:Pfx.exit: special handling for some exception types.New pfx_call(func,*a,**kw) function to concisely wrap single function calls.Release 20210717:
@pfx_method: new optional decorator argument "with_args" to include some or all arguments in the Pfx context.Release 20201227:Pfx: new print=False option to issue a print() or other call on entry to the with-suite eg with Pfx(....,print=verbose).Pfx: print= now also accepts a file-like object.Release 20201105:
@pfx: bugfix for generator functions.Release 20201025:Refactor @pfx using @cs.deco.contextdecorator.New unpfx() function, a crude hack to strip an applpied cs.pfx prefix from a string.XP: just shim cs.x.X as callers expect, toss dubious extra functionality.exception(): plumb keyword arguments.Release 20200517:@pfx: handle normal functions and also generators, improve behaviour with the wrapped docstring.@pfx_method: @pfx for methods.@pfxtag obsoleted by new @pfx.Release 20191004:
@pfx_method: new optionaluse_strparameter to use str(self) instead of type(self).name; now requires @cs.deco.decoratorRelease 20190905:Pfx.exit: simplify prefixify_exc() logic, prefixify all suitable attributes.New @pfx_method decorator for instance methods.Release 20190607:
Pfx.exitimproved exception attribute handling.Release 20190403:
Debugging aid: Pfx.umark: emit stack traceback on format conversion error.Release 20190327:@pfx: setnameon the wrapper function.Bugfix some references to the internal prefixify function.Release 20190324:
Pfx.exit: apply the prefix to all the standard attributes where present, improves some message behaviour for some exception types.Release 20181231:
Bugfix for an infinite regress.Release 20181109:Update @contextmanager formalism to use try/finally for the cleanup phase.New decorator @gen to manage Pfx state across generator iterations; pretty clunky.Better fallback handling.Some docstring updates.Release 20170910:
Slight linting.Release 20170903.1:
corrections to the module docstringRelease 20170903:
Initial release for PyPI.