Revised version, completing a bunch of things that weren't resolved
before. The implementation was removed from the PEP, it's now in the SF patch manager; I'm pretty happy with it! :-)
This commit is contained in:
Guido van Rossum
parent
5d702e543f
commit
aaef244947
274
pep-0230.txt
274
pep-0230.txt
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@ -190,162 +190,146 @@ The Warnings Output Hook
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to sys.stderr, and shows the source line of the filename.
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TO DO
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API For Manipulating Warning Filters
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- There should be a function sys.insertwarningfilter(message,
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category, filename, lineno) that inserts items into the warnings
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filter after some sanity checking.
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sys.filterwarnings(message, category, module, lineno, action)
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- There should be command line options to specify the most common
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filtering actions, which I expect to include at least:
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This checks the types of the arguments and inserts them as a tuple
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in front of the warnings filter.
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- suppress all warnings
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sys.resetwarnings()
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- suppress a particular warning message everywhere
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Reset the warnings filter to empty.
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- suppress all warnings in a particular module
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sys.setupwarnings(args)
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- turn all warnings into exceptions
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Parse command line options and initialize the warnings filter
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accordingly. The argument should be sys.argv[1:] or equivalent.
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Unrecognized options raise getopt.error. The return value is a
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list containing the remaining (non-option) arguments.
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Command Line Syntax
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There should be command line options to specify the most common
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filtering actions, which I expect to include at least:
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- suppress all warnings
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- suppress a particular warning message everywhere
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- suppress all warnings in a particular module
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- turn all warnings into exceptions
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I propose the following command line option syntax:
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-Waction[:message[:category[:module[:lineno]]]]
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Where:
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- 'action' is an abbreviation of one of the allowed actions
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("error", "default", "ignore", "always", "once", or "module")
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- 'message' is a message string; matches warnings whose message
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text is an initial substring of 'message' (matching is
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case-sensitive)
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- 'category' is an abbreviation of a standard warning category
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class name *or* a fully-qualified name for a user-defined
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warning category class of the form [package.]module.classname
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- 'module' is a module name (possibly package.module)
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- 'lineno' is an integral line number
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All parts except 'action' may be omitted, where an empty value
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after stripping whitespace is the same as an omitted value.
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Each -W option results into a call to sys.filterwarnings(); thus
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later -W options override earlier -W options for warnings they
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both match.
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Examples:
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-Werror
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Turn all warnings into errors
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-Wall
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Show all warnings
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-Wignore
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Ignore all warnings
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-Wi:hello
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Ignore warnings whose message text starts with "hello"
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-We::Deprecation
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Turn deprecation warnings into errors
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-Wi:::spam:10
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Ignore all warnings on line 10 of module spam
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-Wi:::spam -Wd:::spam:10
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Ignore all warnings in module spam except on line 10
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-We::Deprecation -Wd::Deprecation:spam
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Turn deprecation warnings into errors except in module spam
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Open Issues
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Some open issues off the top of my head:
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- The proposal has all the Python API functions in the sys module,
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except that the warning categories are in the warnings module.
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Perhaps everything should be in the warnings module (like the
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prototype implementation)? Or perhaps warn() should be promoted
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to a built-in (i.e. in the __builtin__ module)?
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- It's tempting to leave the implementation in Python and add an
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absolute minimal amount of C code, only to make the standard
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warning categories available from C code. The Py_Warn()
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function could call warnings.warn(). Similarly, the Python
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main() function could collect -W options and pass them to
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warnings.setupwarnings().
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- The prototype implements a third argument to warn():
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warn(message, category=UserWarning, level=1)
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The 'level' argument could be used by wrapper functions written
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in Python, like this:
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def deprecation(message):
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warn(message, DeprecationWarning, level=2)
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This makes the warning refer to the deprecation()'s caller,
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rather than to the source of deprecation() itself (the latter
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would defeat the purpose of the warning message).
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- The proposed command line syntax is ugly (although the simple
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cases aren't so bad: -Werror, -Wignore, etc.). Anybody got a
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better idea?
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- I'm a bit worried that the filter specifications are too
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complex. Perhaps filtering only on category and module (not on
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message text and line number) would be enough?
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- There's a bit of confusion between module names and file names.
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The reporting uses file names, but the filter specification uses
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module names. Maybe it should allow filenames as well?
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- I'm not at all convinced that packages are handled right.
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- Better names for the various API functions?
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Implementation
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Here is a mostly functional implementation:
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"""Prototype implementation of sys.warn() and related stuff."""
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import sys, re, linecache, getopt
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class Warning(Exception):
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"""Base class for warning categories.
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All warning categories must be subclasses of this.
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"""
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pass
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class UserWarning(Warning):
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"""Base class for warnings generated by user code."""
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pass
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class DeprecationWarning(Warning):
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"""Base class for warnings about deprecated features."""
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pass
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class SyntaxWarning(Warning):
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"""Base class for warnings about dubious syntax."""
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pass
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defaultaction = "default"
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filter = []
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onceregistry = {}
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def warn(message, category=None, level=1):
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"""Issue a warning, or maybe ignore it or raise an exception."""
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# Check category argument
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if category is None:
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category = UserWarning
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assert issubclass(category, Warning)
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# Get context information
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caller = sys._getframe(level)
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globals = caller.f_globals
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lineno = caller.f_lineno
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module = globals['__name__']
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filename = globals.get('__file__')
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if not filename:
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if module == "__main__":
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filename = sys.argv[0]
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if not filename:
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filename = module
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# Quick test for common case
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registry = globals.setdefault("__warningregistry__", {})
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key = (message, category, lineno)
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if registry.get(key):
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return
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# Search the filter
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for msg, cat, mod, ln, action in filter:
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if (re.match(msg, message) and
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issubclass(category, cat) and
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re.match(mod, module) and
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(ln == 0 or lineno == ln)):
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break
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else:
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action = defaultaction
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# Early exit actions
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if action == "ignore":
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registry[key] = 1
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return
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if action == "error":
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raise category(message)
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# Other actions
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if action == "once":
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registry[key] = 1
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oncekey = (message, category)
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if onceregistry.get(oncekey):
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return
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onceregistry[oncekey] = 1
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elif action == "always":
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pass
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elif action == "module":
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registry[key] = 1
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altkey = (message, category, 0)
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if registry.get(altkey):
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return
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registry[altkey] = 1
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elif action == "default":
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registry[key] = 1
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else:
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# Unrecognized actions are errors
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raise RuntimeError(
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"Unrecognized action (%s) in warnings.filter:\n %s" %
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(`action`, str((cat, msg, mod, ln, action))))
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# Print message and context
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showwarning(message, category, filename, lineno)
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def showwarning(message, category, filename, lineno):
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print >>sys.stderr, "%s:%s: %s: %s" % (filename, lineno,
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category.__name__, message)
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line = linecache.getline(filename, lineno).strip()
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if line:
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print >>sys.stderr, " " + line
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def setupfilter(args):
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"""Set up the warnings filter based upon command line options.
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Return remaining command line arguments.
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Raise getopt.error if an unrecognized option is found.
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"""
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opts, args = getopt.getop(args, "")
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return args
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# Self-test
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def _test():
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hello = "hello world"
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warn(hello)
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warn(hello, UserWarning)
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warn(hello, DeprecationWarning)
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for i in range(3):
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warn(hello)
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filter.append(("", Warning, "", 0, "error"))
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try:
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warn(hello)
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except Exception, msg:
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print "Caught", msg.__class__.__name__ + ":", msg
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else:
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print "No exception"
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filter[:] = []
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filter.append(("", Warning, "", 0, "booh"))
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try:
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warn(hello)
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except Exception, msg:
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print "Caught", msg.__class__.__name__ + ":", msg
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else:
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print "No exception"
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if __name__ == "__main__":
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args = setupfilter(sys.argv[1:])
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_test()
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Here's a prototype implementation:
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http://sourceforge.net/patch/?func=detailpatch&patch_id=102715&group_id=5470
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Local Variables:
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