# -*- test-case-name: twisted.test.test_reflect -*-
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
"""
Standardized versions of various cool and/or strange things that you can do
with Python's reflection capabilities.
"""
from __future__ import division, absolute_import, print_function
import sys
import types
import os
import pickle
import weakref
import re
import traceback
from collections import deque
RegexType = type(re.compile(""))
from twisted.python.compat import reraise, nativeString, NativeStringIO
from twisted.python.compat import _PY3
from twisted.python import compat
from twisted.python.deprecate import _fullyQualifiedName as fullyQualifiedName
from twisted.python._oldstyle import _oldStyle
def prefixedMethodNames(classObj, prefix):
"""
Given a class object C{classObj}, returns a list of method names that match
the string C{prefix}.
@param classObj: A class object from which to collect method names.
@param prefix: A native string giving a prefix. Each method with a name
which begins with this prefix will be returned.
@type prefix: L{str}
@return: A list of the names of matching methods of C{classObj} (and base
classes of C{classObj}).
@rtype: L{list} of L{str}
"""
dct = {}
addMethodNamesToDict(classObj, dct, prefix)
return list(dct.keys())
def addMethodNamesToDict(classObj, dict, prefix, baseClass=None):
"""
This goes through C{classObj} (and its bases) and puts method names
starting with 'prefix' in 'dict' with a value of 1. if baseClass isn't
None, methods will only be added if classObj is-a baseClass
If the class in question has the methods 'prefix_methodname' and
'prefix_methodname2', the resulting dict should look something like:
{"methodname": 1, "methodname2": 1}.
@param classObj: A class object from which to collect method names.
@param dict: A L{dict} which will be updated with the results of the
accumulation. Items are added to this dictionary, with method names as
keys and C{1} as values.
@type dict: L{dict}
@param prefix: A native string giving a prefix. Each method of C{classObj}
(and base classes of C{classObj}) with a name which begins with this
prefix will be returned.
@type prefix: L{str}
@param baseClass: A class object at which to stop searching upwards for new
methods. To collect all method names, do not pass a value for this
parameter.
@return: L{None}
"""
for base in classObj.__bases__:
addMethodNamesToDict(base, dict, prefix, baseClass)
if baseClass is None or baseClass in classObj.__bases__:
for name, method in classObj.__dict__.items():
optName = name[len(prefix):]
if ((type(method) is types.FunctionType)
and (name[:len(prefix)] == prefix)
and (len(optName))):
dict[optName] = 1
def prefixedMethods(obj, prefix=''):
"""
Given an object C{obj}, returns a list of method objects that match the
string C{prefix}.
@param obj: An arbitrary object from which to collect methods.
@param prefix: A native string giving a prefix. Each method of C{obj} with
a name which begins with this prefix will be returned.
@type prefix: L{str}
@return: A list of the matching method objects.
@rtype: L{list}
"""
dct = {}
accumulateMethods(obj, dct, prefix)
return list(dct.values())
def accumulateMethods(obj, dict, prefix='', curClass=None):
"""
Given an object C{obj}, add all methods that begin with C{prefix}.
@param obj: An arbitrary object to collect methods from.
@param dict: A L{dict} which will be updated with the results of the
accumulation. Items are added to this dictionary, with method names as
keys and corresponding instance method objects as values.
@type dict: L{dict}
@param prefix: A native string giving a prefix. Each method of C{obj} with
a name which begins with this prefix will be returned.
@type prefix: L{str}
@param curClass: The class in the inheritance hierarchy at which to start
collecting methods. Collection proceeds up. To collect all methods
from C{obj}, do not pass a value for this parameter.
@return: L{None}
"""
if not curClass:
curClass = obj.__class__
for base in curClass.__bases__:
# The implementation of the object class is different on PyPy vs.
# CPython. This has the side effect of making accumulateMethods()
# pick up object methods from all new-style classes -
# such as __getattribute__, etc.
# If we ignore 'object' when accumulating methods, we can get
# consistent behavior on Pypy and CPython.
if base is not object:
accumulateMethods(obj, dict, prefix, base)
for name, method in curClass.__dict__.items():
optName = name[len(prefix):]
if ((type(method) is types.FunctionType)
and (name[:len(prefix)] == prefix)
and (len(optName))):
dict[optName] = getattr(obj, name)
def namedModule(name):
"""
Return a module given its name.
"""
topLevel = __import__(name)
packages = name.split(".")[1:]
m = topLevel
for p in packages:
m = getattr(m, p)
return m
def namedObject(name):
"""
Get a fully named module-global object.
"""
classSplit = name.split('.')
module = namedModule('.'.join(classSplit[:-1]))
return getattr(module, classSplit[-1])
namedClass = namedObject # backwards compat
def requireModule(name, default=None):
"""
Try to import a module given its name, returning C{default} value if
C{ImportError} is raised during import.
@param name: Module name as it would have been passed to C{import}.
@type name: C{str}.
@param default: Value returned in case C{ImportError} is raised while
importing the module.
@return: Module or default value.
"""
try:
return namedModule(name)
except ImportError:
return default
class _NoModuleFound(Exception):
"""
No module was found because none exists.
"""
class InvalidName(ValueError):
"""
The given name is not a dot-separated list of Python objects.
"""
class ModuleNotFound(InvalidName):
"""
The module associated with the given name doesn't exist and it can't be
imported.
"""
class ObjectNotFound(InvalidName):
"""
The object associated with the given name doesn't exist and it can't be
imported.
"""
def _importAndCheckStack(importName):
"""
Import the given name as a module, then walk the stack to determine whether
the failure was the module not existing, or some code in the module (for
example a dependent import) failing. This can be helpful to determine
whether any actual application code was run. For example, to distiguish
administrative error (entering the wrong module name), from programmer
error (writing buggy code in a module that fails to import).
@param importName: The name of the module to import.
@type importName: C{str}
@raise Exception: if something bad happens. This can be any type of
exception, since nobody knows what loading some arbitrary code might
do.
@raise _NoModuleFound: if no module was found.
"""
try:
return __import__(importName)
except ImportError:
excType, excValue, excTraceback = sys.exc_info()
while excTraceback:
execName = excTraceback.tb_frame.f_globals["__name__"]
# in Python 2 execName is None when an ImportError is encountered,
# where in Python 3 execName is equal to the importName.
if execName is None or execName == importName:
reraise(excValue, excTraceback)
excTraceback = excTraceback.tb_next
raise _NoModuleFound()
def namedAny(name):
"""
Retrieve a Python object by its fully qualified name from the global Python
module namespace. The first part of the name, that describes a module,
will be discovered and imported. Each subsequent part of the name is
treated as the name of an attribute of the object specified by all of the
name which came before it. For example, the fully-qualified name of this
object is 'twisted.python.reflect.namedAny'.
@type name: L{str}
@param name: The name of the object to return.
@raise InvalidName: If the name is an empty string, starts or ends with
a '.', or is otherwise syntactically incorrect.
@raise ModuleNotFound: If the name is syntactically correct but the
module it specifies cannot be imported because it does not appear to
exist.
@raise ObjectNotFound: If the name is syntactically correct, includes at
least one '.', but the module it specifies cannot be imported because
it does not appear to exist.
@raise AttributeError: If an attribute of an object along the way cannot be
accessed, or a module along the way is not found.
@return: the Python object identified by 'name'.
"""
if not name:
raise InvalidName('Empty module name')
names = name.split('.')
# if the name starts or ends with a '.' or contains '..', the __import__
# will raise an 'Empty module name' error. This will provide a better error
# message.
if '' in names:
raise InvalidName(
"name must be a string giving a '.'-separated list of Python "
"identifiers, not %r" % (name,))
topLevelPackage = None
moduleNames = names[:]
while not topLevelPackage:
if moduleNames:
trialname = '.'.join(moduleNames)
try:
topLevelPackage = _importAndCheckStack(trialname)
except _NoModuleFound:
moduleNames.pop()
else:
if len(names) == 1:
raise ModuleNotFound("No module named %r" % (name,))
else:
raise ObjectNotFound('%r does not name an object' % (name,))
obj = topLevelPackage
for n in names[1:]:
obj = getattr(obj, n)
return obj
def filenameToModuleName(fn):
"""
Convert a name in the filesystem to the name of the Python module it is.
This is aggressive about getting a module name back from a file; it will
always return a string. Aggressive means 'sometimes wrong'; it won't look
at the Python path or try to do any error checking: don't use this method
unless you already know that the filename you're talking about is a Python
module.
@param fn: A filesystem path to a module or package; C{bytes} on Python 2,
C{bytes} or C{unicode} on Python 3.
@return: A hopefully importable module name.
@rtype: C{str}
"""
if isinstance(fn, bytes):
initPy = b"__init__.py"
else:
initPy = "__init__.py"
fullName = os.path.abspath(fn)
base = os.path.basename(fn)
if not base:
# this happens when fn ends with a path separator, just skit it
base = os.path.basename(fn[:-1])
modName = nativeString(os.path.splitext(base)[0])
while 1:
fullName = os.path.dirname(fullName)
if os.path.exists(os.path.join(fullName, initPy)):
modName = "%s.%s" % (
nativeString(os.path.basename(fullName)),
nativeString(modName))
else:
break
return modName
def qual(clazz):
"""
Return full import path of a class.
"""
return clazz.__module__ + '.' + clazz.__name__
def _determineClass(x):
try:
return x.__class__
except:
return type(x)
def _determineClassName(x):
c = _determineClass(x)
try:
return c.__name__
except:
try:
return str(c)
except:
return '<BROKEN CLASS AT 0x%x>' % id(c)
def _safeFormat(formatter, o):
"""
Helper function for L{safe_repr} and L{safe_str}.
Called when C{repr} or C{str} fail. Returns a string containing info about
C{o} and the latest exception.
@param formatter: C{str} or C{repr}.
@type formatter: C{type}
@param o: Any object.
@rtype: C{str}
@return: A string containing information about C{o} and the raised
exception.
"""
io = NativeStringIO()
traceback.print_exc(file=io)
className = _determineClassName(o)
tbValue = io.getvalue()
return "<%s instance at 0x%x with %s error:\n %s>" % (
className, id(o), formatter.__name__, tbValue)
def safe_repr(o):
"""
Returns a string representation of an object, or a string containing a
traceback, if that object's __repr__ raised an exception.
@param o: Any object.
@rtype: C{str}
"""
try:
return repr(o)
except:
return _safeFormat(repr, o)
def safe_str(o):
"""
Returns a string representation of an object, or a string containing a
traceback, if that object's __str__ raised an exception.
@param o: Any object.
@rtype: C{str}
"""
if _PY3 and isinstance(o, bytes):
# If o is bytes and seems to holds a utf-8 encoded string,
# convert it to str.
try:
return o.decode('utf-8')
except:
pass
try:
return str(o)
except:
return _safeFormat(str, o)
@_oldStyle
class QueueMethod:
"""
I represent a method that doesn't exist yet.
"""
def __init__(self, name, calls):
self.name = name
self.calls = calls
def __call__(self, *args):
self.calls.append((self.name, args))
def fullFuncName(func):
qualName = (str(pickle.whichmodule(func, func.__name__)) + '.' + func.__name__)
if namedObject(qualName) is not func:
raise Exception("Couldn't find %s as %s." % (func, qualName))
return qualName
def getClass(obj):
"""
Return the class or type of object 'obj'.
Returns sensible result for oldstyle and newstyle instances and types.
"""
if hasattr(obj, '__class__'):
return obj.__class__
else:
return type(obj)
def accumulateClassDict(classObj, attr, adict, baseClass=None):
"""
Accumulate all attributes of a given name in a class hierarchy into a single dictionary.
Assuming all class attributes of this name are dictionaries.
If any of the dictionaries being accumulated have the same key, the
one highest in the class hierarchy wins.
(XXX: If \"highest\" means \"closest to the starting class\".)
Ex::
class Soy:
properties = {\"taste\": \"bland\"}
class Plant:
properties = {\"colour\": \"green\"}
class Seaweed(Plant):
pass
class Lunch(Soy, Seaweed):
properties = {\"vegan\": 1 }
dct = {}
accumulateClassDict(Lunch, \"properties\", dct)
print(dct)
{\"taste\": \"bland\", \"colour\": \"green\", \"vegan\": 1}
"""
for base in classObj.__bases__:
accumulateClassDict(base, attr, adict)
if baseClass is None or baseClass in classObj.__bases__:
adict.update(classObj.__dict__.get(attr, {}))
def accumulateClassList(classObj, attr, listObj, baseClass=None):
"""
Accumulate all attributes of a given name in a class hierarchy into a single list.
Assuming all class attributes of this name are lists.
"""
for base in classObj.__bases__:
accumulateClassList(base, attr, listObj)
if baseClass is None or baseClass in classObj.__bases__:
listObj.extend(classObj.__dict__.get(attr, []))
def isSame(a, b):
return (a is b)
def isLike(a, b):
return (a == b)
def modgrep(goal):
return objgrep(sys.modules, goal, isLike, 'sys.modules')
def isOfType(start, goal):
return ((type(start) is goal) or
(isinstance(start, compat.InstanceType) and
start.__class__ is goal))
def findInstances(start, t):
return objgrep(start, t, isOfType)
if not _PY3:
# The function objgrep() currently doesn't work on Python 3 due to some
# edge cases, as described in #6986.
# twisted.python.reflect is quite important and objgrep is not used in
# Twisted itself, so in #5929, we decided to port everything but objgrep()
# and to finish the porting in #6986
def objgrep(start, goal, eq=isLike, path='', paths=None, seen=None,
showUnknowns=0, maxDepth=None):
"""
An insanely CPU-intensive process for finding stuff.
"""
if paths is None:
paths = []
if seen is None:
seen = {}
if eq(start, goal):
paths.append(path)
if id(start) in seen:
if seen[id(start)] is start:
return
if maxDepth is not None:
if maxDepth == 0:
return
maxDepth -= 1
seen[id(start)] = start
# Make an alias for those arguments which are passed recursively to
# objgrep for container objects.
args = (paths, seen, showUnknowns, maxDepth)
if isinstance(start, dict):
for k, v in start.items():
objgrep(k, goal, eq, path+'{'+repr(v)+'}', *args)
objgrep(v, goal, eq, path+'['+repr(k)+']', *args)
elif isinstance(start, (list, tuple, deque)):
for idx, _elem in enumerate(start):
objgrep(start[idx], goal, eq, path+'['+str(idx)+']', *args)
elif isinstance(start, types.MethodType):
objgrep(start.__self__, goal, eq, path+'.__self__', *args)
objgrep(start.__func__, goal, eq, path+'.__func__', *args)
objgrep(start.__self__.__class__, goal, eq,
path+'.__self__.__class__', *args)
elif hasattr(start, '__dict__'):
for k, v in start.__dict__.items():
objgrep(v, goal, eq, path+'.'+k, *args)
if isinstance(start, compat.InstanceType):
objgrep(start.__class__, goal, eq, path+'.__class__', *args)
elif isinstance(start, weakref.ReferenceType):
objgrep(start(), goal, eq, path+'()', *args)
elif (isinstance(start, (compat.StringType,
int, types.FunctionType,
types.BuiltinMethodType, RegexType, float,
type(None), compat.FileType)) or
type(start).__name__ in ('wrapper_descriptor',
'method_descriptor', 'member_descriptor',
'getset_descriptor')):
pass
elif showUnknowns:
print('unknown type', type(start), start)
return paths
__all__ = [
'InvalidName', 'ModuleNotFound', 'ObjectNotFound',
'QueueMethod',
'namedModule', 'namedObject', 'namedClass', 'namedAny', 'requireModule',
'safe_repr', 'safe_str', 'prefixedMethodNames', 'addMethodNamesToDict',
'prefixedMethods', 'accumulateMethods', 'fullFuncName', 'qual', 'getClass',
'accumulateClassDict', 'accumulateClassList', 'isSame', 'isLike',
'modgrep', 'isOfType', 'findInstances', 'objgrep', 'filenameToModuleName',
'fullyQualifiedName']
if _PY3:
# This is to be removed when fixing #6986
__all__.remove('objgrep')