cpython/Lib/warnings.py

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"""Python part of the warnings subsystem."""
# Note: function level imports should *not* be used
# in this module as it may cause import lock deadlock.
# See bug 683658.
import sys, types
import linecache
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__all__ = ["warn", "showwarning", "formatwarning", "filterwarnings",
"resetwarnings"]
# filters contains a sequence of filter 5-tuples
# The components of the 5-tuple are:
# - an action: error, ignore, always, default, module, or once
# - a compiled regex that must match the warning message
# - a class representing the warning category
# - a compiled regex that must match the module that is being warned
# - a line number for the line being warning, or 0 to mean any line
# If either if the compiled regexs are None, match anything.
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filters = []
defaultaction = "default"
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onceregistry = {}
def warn(message, category=None, stacklevel=1):
"""Issue a warning, or maybe ignore it or raise an exception."""
# Check if message is already a Warning object
if isinstance(message, Warning):
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category = message.__class__
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# Check category argument
if category is None:
category = UserWarning
assert issubclass(category, Warning)
# Get context information
try:
caller = sys._getframe(stacklevel)
except ValueError:
globals = sys.__dict__
lineno = 1
else:
globals = caller.f_globals
lineno = caller.f_lineno
if '__name__' in globals:
module = globals['__name__']
else:
module = "<string>"
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filename = globals.get('__file__')
if filename:
fnl = filename.lower()
if fnl.endswith(".pyc") or fnl.endswith(".pyo"):
filename = filename[:-1]
else:
if module == "__main__":
try:
filename = sys.argv[0]
except AttributeError:
# embedded interpreters don't have sys.argv, see bug #839151
filename = '__main__'
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if not filename:
filename = module
registry = globals.setdefault("__warningregistry__", {})
warn_explicit(message, category, filename, lineno, module, registry)
def warn_explicit(message, category, filename, lineno,
module=None, registry=None):
if module is None:
module = filename
if module[-3:].lower() == ".py":
module = module[:-3] # XXX What about leading pathname?
if registry is None:
registry = {}
if isinstance(message, Warning):
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text = str(message)
category = message.__class__
else:
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text = message
message = category(message)
key = (text, category, lineno)
# Quick test for common case
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if registry.get(key):
return
# Search the filters
for item in filters:
action, msg, cat, mod, ln = item
if ((msg is None or msg.match(text)) and
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issubclass(category, cat) and
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(mod is None or mod.match(module)) and
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(ln == 0 or lineno == ln)):
break
else:
action = defaultaction
# Early exit actions
if action == "ignore":
registry[key] = 1
return
if action == "error":
raise message
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# Other actions
if action == "once":
registry[key] = 1
oncekey = (text, category)
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if onceregistry.get(oncekey):
return
onceregistry[oncekey] = 1
elif action == "always":
pass
elif action == "module":
registry[key] = 1
altkey = (text, category, 0)
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if registry.get(altkey):
return
registry[altkey] = 1
elif action == "default":
registry[key] = 1
else:
# Unrecognized actions are errors
raise RuntimeError(
"Unrecognized action (%r) in warnings.filters:\n %s" %
(action, item))
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# Print message and context
showwarning(message, category, filename, lineno)
def showwarning(message, category, filename, lineno, file=None):
"""Hook to write a warning to a file; replace if you like."""
if file is None:
file = sys.stderr
try:
file.write(formatwarning(message, category, filename, lineno))
except IOError:
pass # the file (probably stderr) is invalid - this warning gets lost.
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def formatwarning(message, category, filename, lineno):
"""Function to format a warning the standard way."""
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s = "%s:%s: %s: %s\n" % (filename, lineno, category.__name__, message)
line = linecache.getline(filename, lineno).strip()
if line:
s = s + " " + line + "\n"
return s
def filterwarnings(action, message="", category=Warning, module="", lineno=0,
append=0):
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"""Insert an entry into the list of warnings filters (at the front).
Use assertions to check that all arguments have the right type."""
import re
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assert action in ("error", "ignore", "always", "default", "module",
"once"), "invalid action: %r" % (action,)
assert isinstance(message, basestring), "message must be a string"
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assert isinstance(category, types.ClassType), "category must be a class"
assert issubclass(category, Warning), "category must be a Warning subclass"
assert isinstance(module, basestring), "module must be a string"
assert isinstance(lineno, int) and lineno >= 0, \
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"lineno must be an int >= 0"
item = (action, re.compile(message, re.I), category,
re.compile(module), lineno)
if append:
filters.append(item)
else:
filters.insert(0, item)
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def simplefilter(action, category=Warning, lineno=0, append=0):
"""Insert a simple entry into the list of warnings filters (at the front).
A simple filter matches all modules and messages.
"""
assert action in ("error", "ignore", "always", "default", "module",
"once"), "invalid action: %r" % (action,)
assert isinstance(lineno, int) and lineno >= 0, \
"lineno must be an int >= 0"
item = (action, None, category, None, lineno)
if append:
filters.append(item)
else:
filters.insert(0, item)
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def resetwarnings():
"""Clear the list of warning filters, so that no filters are active."""
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filters[:] = []
class _OptionError(Exception):
"""Exception used by option processing helpers."""
pass
# Helper to process -W options passed via sys.warnoptions
def _processoptions(args):
for arg in args:
try:
_setoption(arg)
except _OptionError, msg:
print >>sys.stderr, "Invalid -W option ignored:", msg
# Helper for _processoptions()
def _setoption(arg):
import re
parts = arg.split(':')
if len(parts) > 5:
raise _OptionError("too many fields (max 5): %r" % (arg,))
while len(parts) < 5:
parts.append('')
action, message, category, module, lineno = [s.strip()
for s in parts]
action = _getaction(action)
message = re.escape(message)
category = _getcategory(category)
module = re.escape(module)
if module:
module = module + '$'
if lineno:
try:
lineno = int(lineno)
if lineno < 0:
raise ValueError
except (ValueError, OverflowError):
raise _OptionError("invalid lineno %r" % (lineno,))
else:
lineno = 0
filterwarnings(action, message, category, module, lineno)
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# Helper for _setoption()
def _getaction(action):
if not action:
return "default"
if action == "all": return "always" # Alias
for a in ('default', 'always', 'ignore', 'module', 'once', 'error'):
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if a.startswith(action):
return a
raise _OptionError("invalid action: %r" % (action,))
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# Helper for _setoption()
def _getcategory(category):
import re
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if not category:
return Warning
if re.match("^[a-zA-Z0-9_]+$", category):
try:
cat = eval(category)
except NameError:
raise _OptionError("unknown warning category: %r" % (category,))
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else:
i = category.rfind(".")
module = category[:i]
klass = category[i+1:]
try:
m = __import__(module, None, None, [klass])
except ImportError:
raise _OptionError("invalid module name: %r" % (module,))
try:
cat = getattr(m, klass)
except AttributeError:
raise _OptionError("unknown warning category: %r" % (category,))
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if (not isinstance(cat, types.ClassType) or
not issubclass(cat, Warning)):
raise _OptionError("invalid warning category: %r" % (category,))
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return cat
# Module initialization
_processoptions(sys.warnoptions)
# XXX OverflowWarning should go away for Python 2.5.
simplefilter("ignore", category=OverflowWarning, append=1)
simplefilter("ignore", category=PendingDeprecationWarning, append=1)