Lib/inspect.py

   1 """Get useful information from live Python objects.
   2
   3 This module encapsulates the interface provided by the internal special
   4 attributes (func_*, co_*, im_*, tb_*, etc.) in a friendlier fashion.
   5 It also provides some help for examining source code and class layout.
   6
   7 Here are some of the useful functions provided by this module:
   8
   9     ismodule(), isclass(), ismethod(), isfunction(), istraceback(),
  10         isframe(), iscode(), isbuiltin(), isroutine() - check object types
  11     getmembers() - get members of an object that satisfy a given condition
  12
  13     getfile(), getsourcefile(), getsource() - find an object's source code
  14     getdoc(), getcomments() - get documentation on an object
  15     getmodule() - determine the module that an object came from
  16     getclasstree() - arrange classes so as to represent their hierarchy
  17
  18     getargspec(), getargvalues() - get info about function arguments
  19     formatargspec(), formatargvalues() - format an argument spec
  20     getouterframes(), getinnerframes() - get info about frames
  21     currentframe() - get the current stack frame
  22     stack(), trace() - get info about frames on the stack or in a traceback
  23 """
  24
  25 # This module is in the public domain.  No warranties.
  26
  27 __author__ = 'Ka-Ping Yee <ping@lfw.org>'
  28 __date__ = '1 Jan 2001'
  29
  30 import sys, os, types, string, re, dis, imp, tokenize
  31
  32 # ----------------------------------------------------------- type-checking
  33 def ismodule(object):
  34     """Return true if the object is a module.
  35
  36     Module objects provide these attributes:
  37         __doc__         documentation string
  38         __file__        filename (missing for built-in modules)"""
  39     return isinstance(object, types.ModuleType)
  40
  41 def isclass(object):
  42     """Return true if the object is a class.
  43
  44     Class objects provide these attributes:
  45         __doc__         documentation string
  46         __module__      name of module in which this class was defined"""
  47     return isinstance(object, types.ClassType) or hasattr(object, '__bases__')
  48
  49 def ismethod(object):
  50     """Return true if the object is an instance method.
  51
  52     Instance method objects provide these attributes:
  53         __doc__         documentation string
  54         __name__        name with which this method was defined
  55         im_class        class object in which this method belongs
  56         im_func         function object containing implementation of method
  57         im_self         instance to which this method is bound, or None"""
  58     return isinstance(object, types.MethodType)
  59
  60 def ismethoddescriptor(object):
  61     """Return true if the object is a method descriptor.
  62
  63     But not if ismethod() or isclass() or isfunction() are true.
  64
  65     This is new in Python 2.2, and, for example, is true of int.__add__.
  66     An object passing this test has a __get__ attribute but not a __set__
  67     attribute, but beyond that the set of attributes varies.  __name__ is
  68     usually sensible, and __doc__ often is.
  69
  70     Methods implemented via descriptors that also pass one of the other
  71     tests return false from the ismethoddescriptor() test, simply because
  72     the other tests promise more -- you can, e.g., count on having the
  73     im_func attribute (etc) when an object passes ismethod()."""
  74     return (hasattr(object, "__get__")
  75             and not hasattr(object, "__set__") # else it's a data descriptor
  76             and not ismethod(object)           # mutual exclusion
  77             and not isfunction(object)
  78             and not isclass(object))
  79
  80 def isfunction(object):
  81     """Return true if the object is a user-defined function.
  82
  83     Function objects provide these attributes:
  84         __doc__         documentation string
  85         __name__        name with which this function was defined
  86         func_code       code object containing compiled function bytecode
  87         func_defaults   tuple of any default values for arguments
  88         func_doc        (same as __doc__)
  89         func_globals    global namespace in which this function was defined
  90         func_name       (same as __name__)"""
  91     return isinstance(object, types.FunctionType)
  92
  93 def istraceback(object):
  94     """Return true if the object is a traceback.
  95
  96     Traceback objects provide these attributes:
  97         tb_frame        frame object at this level
  98         tb_lasti        index of last attempted instruction in bytecode
  99         tb_lineno       current line number in Python source code
 100         tb_next         next inner traceback object (called by this level)"""
 101     return isinstance(object, types.TracebackType)
 102
 103 def isframe(object):
 104     """Return true if the object is a frame object.
 105
 106     Frame objects provide these attributes:
 107         f_back          next outer frame object (this frame's caller)
 108         f_builtins      built-in namespace seen by this frame
 109         f_code          code object being executed in this frame
 110         f_exc_traceback traceback if raised in this frame, or None
 111         f_exc_type      exception type if raised in this frame, or None
 112         f_exc_value     exception value if raised in this frame, or None
 113         f_globals       global namespace seen by this frame
 114         f_lasti         index of last attempted instruction in bytecode
 115         f_lineno        current line number in Python source code
 116         f_locals        local namespace seen by this frame
 117         f_restricted    0 or 1 if frame is in restricted execution mode
 118         f_trace         tracing function for this frame, or None"""
 119     return isinstance(object, types.FrameType)
 120
 121 def iscode(object):
 122     """Return true if the object is a code object.
 123
 124     Code objects provide these attributes:
 125         co_argcount     number of arguments (not including * or ** args)
 126         co_code         string of raw compiled bytecode
 127         co_consts       tuple of constants used in the bytecode
 128         co_filename     name of file in which this code object was created
 129         co_firstlineno  number of first line in Python source code
 130         co_flags        bitmap: 1=optimized | 2=newlocals | 4=*arg | 8=**arg
 131         co_lnotab       encoded mapping of line numbers to bytecode indices
 132         co_name         name with which this code object was defined
 133         co_names        tuple of names of local variables
 134         co_nlocals      number of local variables
 135         co_stacksize    virtual machine stack space required
 136         co_varnames     tuple of names of arguments and local variables"""
 137     return isinstance(object, types.CodeType)
 138
 139 def isbuiltin(object):
 140     """Return true if the object is a built-in function or method.
 141
 142     Built-in functions and methods provide these attributes:
 143         __doc__         documentation string
 144         __name__        original name of this function or method
 145         __self__        instance to which a method is bound, or None"""
 146     return isinstance(object, types.BuiltinFunctionType)
 147
 148 def isroutine(object):
 149     """Return true if the object is any kind of function or method."""
 150     return (isbuiltin(object)
 151             or isfunction(object)
 152             or ismethod(object)
 153             or ismethoddescriptor(object))
 154
 155 def getmembers(object, predicate=None):
 156     """Return all members of an object as (name, value) pairs sorted by name.
 157     Optionally, only return members that satisfy a given predicate."""
 158     results = []
 159     for key in dir(object):
 160         value = getattr(object, key)
 161         if not predicate or predicate(value):
 162             results.append((key, value))
 163     results.sort()
 164     return results
 165
 166 def classify_class_attrs(cls):
 167     """Return list of attribute-descriptor tuples.
 168
 169     For each name in dir(cls), the return list contains a 4-tuple
 170     with these elements:
 171
 172         0. The name (a string).
 173
 174         1. The kind of attribute this is, one of these strings:
 175                'class method'    created via classmethod()
 176                'static method'   created via staticmethod()
 177                'property'        created via property()
 178                'method'          any other flavor of method
 179                'data'            not a method
 180
 181         2. The class which defined this attribute (a class).
 182
 183         3. The object as obtained directly from the defining class's
 184            __dict__, not via getattr.  This is especially important for
 185            data attributes:  C.data is just a data object, but
 186            C.__dict__['data'] may be a data descriptor with additional
 187            info, like a __doc__ string.
 188     """
 189
 190     mro = getmro(cls)
 191     names = dir(cls)
 192     result = []
 193     for name in names:
 194         # Get the object associated with the name.
 195         # Getting an obj from the __dict__ sometimes reveals more than
 196         # using getattr.  Static and class methods are dramatic examples.
 197         if name in cls.__dict__:
 198             obj = cls.__dict__[name]
 199         else:
 200             obj = getattr(cls, name)
 201
 202         # Figure out where it was defined.
 203         # A complication:  static classes in 2.2 copy dict entries from
 204         # bases into derived classes, so it's not enough just to look for
 205         # "the first" class with the name in its dict.  OTOH:
 206         # 1. Some-- but not all --methods in 2.2 come with an __objclass__
 207         #    attr that answers the question directly.
 208         # 2. Some-- but not all --classes in 2.2 have a __defined__ dict
 209         #    saying which names were defined by the class.
 210         homecls = getattr(obj, "__objclass__", None)
 211         if homecls is None:
 212             # Try __defined__.
 213             for base in mro:
 214                 if hasattr(base, "__defined__"):
 215                     if name in base.__defined__:
 216                         homecls = base
 217                         break
 218         if homecls is None:
 219             # Last chance (and first chance for classic classes):  search
 220             # the dicts.
 221             for base in mro:
 222                 if name in base.__dict__:
 223                     homecls = base
 224                     break
 225
 226         # Get the object again, in order to get it from the defining
 227         # __dict__ instead of via getattr (if possible).
 228         if homecls is not None and name in homecls.__dict__:
 229             obj = homecls.__dict__[name]
 230
 231         # Also get the object via getattr.
 232         obj_via_getattr = getattr(cls, name)
 233
 234         # Classify the object.
 235         if isinstance(obj, staticmethod):
 236             kind = "static method"
 237         elif isinstance(obj, classmethod):
 238             kind = "class method"
 239         elif isinstance(obj, property):
 240             kind = "property"
 241         elif (ismethod(obj_via_getattr) or
 242               ismethoddescriptor(obj_via_getattr)):
 243             kind = "method"
 244         else:
 245             kind = "data"
 246
 247         result.append((name, kind, homecls, obj))
 248
 249     return result
 250
 251 # ----------------------------------------------------------- class helpers
 252 def _searchbases(cls, accum):
 253     # Simulate the "classic class" search order.
 254     if cls in accum:
 255         return
 256     accum.append(cls)
 257     for base in cls.__bases__:
 258         _searchbases(base, accum)
 259
 260 def getmro(cls):
 261     "Return tuple of base classes (including cls) in method resolution order."
 262     if hasattr(cls, "__mro__"):
 263         return cls.__mro__
 264     else:
 265         result = []
 266         _searchbases(cls, result)
 267         return tuple(result)
 268
 269 # -------------------------------------------------- source code extraction
 270 def indentsize(line):
 271     """Return the indent size, in spaces, at the start of a line of text."""
 272     expline = string.expandtabs(line)
 273     return len(expline) - len(string.lstrip(expline))
 274
 275 def getdoc(object):
 276     """Get the documentation string for an object.
 277
 278     All tabs are expanded to spaces.  To clean up docstrings that are
 279     indented to line up with blocks of code, any whitespace than can be
 280     uniformly removed from the second line onwards is removed."""
 281     if hasattr(object, '__doc__') and object.__doc__:
 282         lines = string.split(string.expandtabs(object.__doc__), '\n')
 283         margin = None
 284         for line in lines[1:]:
 285             content = len(string.lstrip(line))
 286             if not content: continue
 287             indent = len(line) - content
 288             if margin is None: margin = indent
 289             else: margin = min(margin, indent)
 290         if margin is not None:
 291             for i in range(1, len(lines)): lines[i] = lines[i][margin:]
 292         return string.join(lines, '\n')
 293
 294 def getfile(object):
 295     """Work out which source or compiled file an object was defined in."""
 296     if ismodule(object):
 297         if hasattr(object, '__file__'):
 298             return object.__file__
 299         raise TypeError, 'arg is a built-in module'
 300     if isclass(object):
 301         object = sys.modules.get(object.__module__)
 302         if hasattr(object, '__file__'):
 303             return object.__file__
 304         raise TypeError, 'arg is a built-in class'
 305     if ismethod(object):
 306         object = object.im_func
 307     if isfunction(object):
 308         object = object.func_code
 309     if istraceback(object):
 310         object = object.tb_frame
 311     if isframe(object):
 312         object = object.f_code
 313     if iscode(object):
 314         return object.co_filename
 315     raise TypeError, 'arg is not a module, class, method, ' \
 316                      'function, traceback, frame, or code object'
 317
 318 def getmoduleinfo(path):
 319     """Get the module name, suffix, mode, and module type for a given file."""
 320     filename = os.path.basename(path)
 321     suffixes = map(lambda (suffix, mode, mtype):
 322                    (-len(suffix), suffix, mode, mtype), imp.get_suffixes())
 323     suffixes.sort() # try longest suffixes first, in case they overlap
 324     for neglen, suffix, mode, mtype in suffixes:
 325         if filename[neglen:] == suffix:
 326             return filename[:neglen], suffix, mode, mtype
 327
 328 def getmodulename(path):
 329     """Return the module name for a given file, or None."""
 330     info = getmoduleinfo(path)
 331     if info: return info[0]
 332
 333 def getsourcefile(object):
 334     """Return the Python source file an object was defined in, if it exists."""
 335     filename = getfile(object)
 336     if string.lower(filename[-4:]) in ['.pyc', '.pyo']:
 337         filename = filename[:-4] + '.py'
 338     for suffix, mode, kind in imp.get_suffixes():
 339         if 'b' in mode and string.lower(filename[-len(suffix):]) == suffix:
 340             # Looks like a binary file.  We want to only return a text file.
 341             return None
 342     if os.path.exists(filename):
 343         return filename
 344
 345 def getabsfile(object):
 346     """Return an absolute path to the source or compiled file for an object.
 347
 348     The idea is for each object to have a unique origin, so this routine
 349     normalizes the result as much as possible."""
 350     return os.path.normcase(
 351         os.path.abspath(getsourcefile(object) or getfile(object)))
 352
 353 modulesbyfile = {}
 354
 355 def getmodule(object):
 356     """Return the module an object was defined in, or None if not found."""
 357     if ismodule(object):
 358         return object
 359     if isclass(object):
 360         return sys.modules.get(object.__module__)
 361     try:
 362         file = getabsfile(object)
 363     except TypeError:
 364         return None
 365     if modulesbyfile.has_key(file):
 366         return sys.modules[modulesbyfile[file]]
 367     for module in sys.modules.values():
 368         if hasattr(module, '__file__'):
 369             modulesbyfile[getabsfile(module)] = module.__name__
 370     if modulesbyfile.has_key(file):
 371         return sys.modules[modulesbyfile[file]]
 372     main = sys.modules['__main__']
 373     if hasattr(main, object.__name__):
 374         mainobject = getattr(main, object.__name__)
 375         if mainobject is object:
 376             return main
 377     builtin = sys.modules['__builtin__']
 378     if hasattr(builtin, object.__name__):
 379         builtinobject = getattr(builtin, object.__name__)
 380         if builtinobject is object:
 381             return builtin
 382
 383 def findsource(object):
 384     """Return the entire source file and starting line number for an object.
 385
 386     The argument may be a module, class, method, function, traceback, frame,
 387     or code object.  The source code is returned as a list of all the lines
 388     in the file and the line number indexes a line in that list.  An IOError
 389     is raised if the source code cannot be retrieved."""
 390     try:
 391         file = open(getsourcefile(object))
 392     except (TypeError, IOError):
 393         raise IOError, 'could not get source code'
 394     lines = file.readlines()
 395     file.close()
 396
 397     if ismodule(object):
 398         return lines, 0
 399
 400     if isclass(object):
 401         name = object.__name__
 402         pat = re.compile(r'^\s*class\s*' + name + r'\b')
 403         for i in range(len(lines)):
 404             if pat.match(lines[i]): return lines, i
 405         else: raise IOError, 'could not find class definition'
 406
 407     if ismethod(object):
 408         object = object.im_func
 409     if isfunction(object):
 410         object = object.func_code
 411     if istraceback(object):
 412         object = object.tb_frame
 413     if isframe(object):
 414         object = object.f_code
 415     if iscode(object):
 416         if not hasattr(object, 'co_firstlineno'):
 417             raise IOError, 'could not find function definition'
 418         lnum = object.co_firstlineno - 1
 419         pat = re.compile(r'^\s*def\s')
 420         while lnum > 0:
 421             if pat.match(lines[lnum]): break
 422             lnum = lnum - 1
 423         return lines, lnum
 424
 425 def getcomments(object):
 426     """Get lines of comments immediately preceding an object's source code."""
 427     try: lines, lnum = findsource(object)
 428     except IOError: return None
 429
 430     if ismodule(object):
 431         # Look for a comment block at the top of the file.
 432         start = 0
 433         if lines and lines[0][:2] == '#!': start = 1
 434         while start < len(lines) and string.strip(lines[start]) in ['', '#']:
 435             start = start + 1
 436         if start < len(lines) and lines[start][:1] == '#':
 437             comments = []
 438             end = start
 439             while end < len(lines) and lines[end][:1] == '#':
 440                 comments.append(string.expandtabs(lines[end]))
 441                 end = end + 1
 442             return string.join(comments, '')
 443
 444     # Look for a preceding block of comments at the same indentation.
 445     elif lnum > 0:
 446         indent = indentsize(lines[lnum])
 447         end = lnum - 1
 448         if end >= 0 and string.lstrip(lines[end])[:1] == '#' and \
 449             indentsize(lines[end]) == indent:
 450             comments = [string.lstrip(string.expandtabs(lines[end]))]
 451             if end > 0:
 452                 end = end - 1
 453                 comment = string.lstrip(string.expandtabs(lines[end]))
 454                 while comment[:1] == '#' and indentsize(lines[end]) == indent:
 455                     comments[:0] = [comment]
 456                     end = end - 1
 457                     if end < 0: break
 458                     comment = string.lstrip(string.expandtabs(lines[end]))
 459             while comments and string.strip(comments[0]) == '#':
 460                 comments[:1] = []
 461             while comments and string.strip(comments[-1]) == '#':
 462                 comments[-1:] = []
 463             return string.join(comments, '')
 464
 465 class ListReader:
 466     """Provide a readline() method to return lines from a list of strings."""
 467     def __init__(self, lines):
 468         self.lines = lines
 469         self.index = 0
 470
 471     def readline(self):
 472         i = self.index
 473         if i < len(self.lines):
 474             self.index = i + 1
 475             return self.lines[i]
 476         else: return ''
 477
 478 class EndOfBlock(Exception): pass
 479
 480 class BlockFinder:
 481     """Provide a tokeneater() method to detect the end of a code block."""
 482     def __init__(self):
 483         self.indent = 0
 484         self.started = 0
 485         self.last = 0
 486
 487     def tokeneater(self, type, token, (srow, scol), (erow, ecol), line):
 488         if not self.started:
 489             if type == tokenize.NAME: self.started = 1
 490         elif type == tokenize.NEWLINE:
 491             self.last = srow
 492         elif type == tokenize.INDENT:
 493             self.indent = self.indent + 1
 494         elif type == tokenize.DEDENT:
 495             self.indent = self.indent - 1
 496             if self.indent == 0: raise EndOfBlock, self.last
 497
 498 def getblock(lines):
 499     """Extract the block of code at the top of the given list of lines."""
 500     try:
 501         tokenize.tokenize(ListReader(lines).readline, BlockFinder().tokeneater)
 502     except EndOfBlock, eob:
 503         return lines[:eob.args[0]]
 504
 505 def getsourcelines(object):
 506     """Return a list of source lines and starting line number for an object.
 507
 508     The argument may be a module, class, method, function, traceback, frame,
 509     or code object.  The source code is returned as a list of the lines
 510     corresponding to the object and the line number indicates where in the
 511     original source file the first line of code was found.  An IOError is
 512     raised if the source code cannot be retrieved."""
 513     lines, lnum = findsource(object)
 514
 515     if ismodule(object): return lines, 0
 516     else: return getblock(lines[lnum:]), lnum + 1
 517
 518 def getsource(object):
 519     """Return the text of the source code for an object.
 520
 521     The argument may be a module, class, method, function, traceback, frame,
 522     or code object.  The source code is returned as a single string.  An
 523     IOError is raised if the source code cannot be retrieved."""
 524     lines, lnum = getsourcelines(object)
 525     return string.join(lines, '')
 526
 527 # --------------------------------------------------- class tree extraction
 528 def walktree(classes, children, parent):
 529     """Recursive helper function for getclasstree()."""
 530     results = []
 531     classes.sort(lambda a, b: cmp(a.__name__, b.__name__))
 532     for c in classes:
 533         results.append((c, c.__bases__))
 534         if children.has_key(c):
 535             results.append(walktree(children[c], children, c))
 536     return results
 537
 538 def getclasstree(classes, unique=0):
 539     """Arrange the given list of classes into a hierarchy of nested lists.
 540
 541     Where a nested list appears, it contains classes derived from the class
 542     whose entry immediately precedes the list.  Each entry is a 2-tuple
 543     containing a class and a tuple of its base classes.  If the 'unique'
 544     argument is true, exactly one entry appears in the returned structure
 545     for each class in the given list.  Otherwise, classes using multiple
 546     inheritance and their descendants will appear multiple times."""
 547     children = {}
 548     roots = []
 549     for c in classes:
 550         if c.__bases__:
 551             for parent in c.__bases__:
 552                 if not children.has_key(parent):
 553                     children[parent] = []
 554                 children[parent].append(c)
 555                 if unique and parent in classes: break
 556         elif c not in roots:
 557             roots.append(c)
 558     for parent in children.keys():
 559         if parent not in classes:
 560             roots.append(parent)
 561     return walktree(roots, children, None)
 562
 563 # ------------------------------------------------ argument list extraction
 564 # These constants are from Python's compile.h.
 565 CO_OPTIMIZED, CO_NEWLOCALS, CO_VARARGS, CO_VARKEYWORDS = 1, 2, 4, 8
 566
 567 def getargs(co):
 568     """Get information about the arguments accepted by a code object.
 569
 570     Three things are returned: (args, varargs, varkw), where 'args' is
 571     a list of argument names (possibly containing nested lists), and
 572     'varargs' and 'varkw' are the names of the * and ** arguments or None."""
 573     if not iscode(co): raise TypeError, 'arg is not a code object'
 574
 575     code = co.co_code
 576     nargs = co.co_argcount
 577     names = co.co_varnames
 578     args = list(names[:nargs])
 579     step = 0
 580
 581     # The following acrobatics are for anonymous (tuple) arguments.
 582     for i in range(nargs):
 583         if args[i][:1] in ['', '.']:
 584             stack, remain, count = [], [], []
 585             while step < len(code):
 586                 op = ord(code[step])
 587                 step = step + 1
 588                 if op >= dis.HAVE_ARGUMENT:
 589                     opname = dis.opname[op]
 590                     value = ord(code[step]) + ord(code[step+1])*256
 591                     step = step + 2
 592                     if opname in ['UNPACK_TUPLE', 'UNPACK_SEQUENCE']:
 593                         remain.append(value)
 594                         count.append(value)
 595                     elif opname == 'STORE_FAST':
 596                         stack.append(names[value])
 597                         remain[-1] = remain[-1] - 1
 598                         while remain[-1] == 0:
 599                             remain.pop()
 600                             size = count.pop()
 601                             stack[-size:] = [stack[-size:]]
 602                             if not remain: break
 603                             remain[-1] = remain[-1] - 1
 604                         if not remain: break
 605             args[i] = stack[0]
 606
 607     varargs = None
 608     if co.co_flags & CO_VARARGS:
 609         varargs = co.co_varnames[nargs]
 610         nargs = nargs + 1
 611     varkw = None
 612     if co.co_flags & CO_VARKEYWORDS:
 613         varkw = co.co_varnames[nargs]
 614     return args, varargs, varkw
 615
 616 def getargspec(func):
 617     """Get the names and default values of a function's arguments.
 618
 619     A tuple of four things is returned: (args, varargs, varkw, defaults).
 620     'args' is a list of the argument names (it may contain nested lists).
 621     'varargs' and 'varkw' are the names of the * and ** arguments or None.
 622     'defaults' is an n-tuple of the default values of the last n arguments."""
 623     if not isfunction(func): raise TypeError, 'arg is not a Python function'
 624     args, varargs, varkw = getargs(func.func_code)
 625     return args, varargs, varkw, func.func_defaults
 626
 627 def getargvalues(frame):
 628     """Get information about arguments passed into a particular frame.
 629
 630     A tuple of four things is returned: (args, varargs, varkw, locals).
 631     'args' is a list of the argument names (it may contain nested lists).
 632     'varargs' and 'varkw' are the names of the * and ** arguments or None.
 633     'locals' is the locals dictionary of the given frame."""
 634     args, varargs, varkw = getargs(frame.f_code)
 635     return args, varargs, varkw, frame.f_locals
 636
 637 def joinseq(seq):
 638     if len(seq) == 1:
 639         return '(' + seq[0] + ',)'
 640     else:
 641         return '(' + string.join(seq, ', ') + ')'
 642
 643 def strseq(object, convert, join=joinseq):
 644     """Recursively walk a sequence, stringifying each element."""
 645     if type(object) in [types.ListType, types.TupleType]:
 646         return join(map(lambda o, c=convert, j=join: strseq(o, c, j), object))
 647     else:
 648         return convert(object)
 649
 650 def formatargspec(args, varargs=None, varkw=None, defaults=None,
 651                   formatarg=str,
 652                   formatvarargs=lambda name: '*' + name,
 653                   formatvarkw=lambda name: '**' + name,
 654                   formatvalue=lambda value: '=' + repr(value),
 655                   join=joinseq):
 656     """Format an argument spec from the 4 values returned by getargspec.
 657
 658     The first four arguments are (args, varargs, varkw, defaults).  The
 659     other four arguments are the corresponding optional formatting functions
 660     that are called to turn names and values into strings.  The ninth
 661     argument is an optional function to format the sequence of arguments."""
 662     specs = []
 663     if defaults:
 664         firstdefault = len(args) - len(defaults)
 665     for i in range(len(args)):
 666         spec = strseq(args[i], formatarg, join)
 667         if defaults and i >= firstdefault:
 668             spec = spec + formatvalue(defaults[i - firstdefault])
 669         specs.append(spec)
 670     if varargs:
 671         specs.append(formatvarargs(varargs))
 672     if varkw:
 673         specs.append(formatvarkw(varkw))
 674     return '(' + string.join(specs, ', ') + ')'
 675
 676 def formatargvalues(args, varargs, varkw, locals,
 677                     formatarg=str,
 678                     formatvarargs=lambda name: '*' + name,
 679                     formatvarkw=lambda name: '**' + name,
 680                     formatvalue=lambda value: '=' + repr(value),
 681                     join=joinseq):
 682     """Format an argument spec from the 4 values returned by getargvalues.
 683
 684     The first four arguments are (args, varargs, varkw, locals).  The
 685     next four arguments are the corresponding optional formatting functions
 686     that are called to turn names and values into strings.  The ninth
 687     argument is an optional function to format the sequence of arguments."""
 688     def convert(name, locals=locals,
 689                 formatarg=formatarg, formatvalue=formatvalue):
 690         return formatarg(name) + formatvalue(locals[name])
 691     specs = []
 692     for i in range(len(args)):
 693         specs.append(strseq(args[i], convert, join))
 694     if varargs:
 695         specs.append(formatvarargs(varargs) + formatvalue(locals[varargs]))
 696     if varkw:
 697         specs.append(formatvarkw(varkw) + formatvalue(locals[varkw]))
 698     return '(' + string.join(specs, ', ') + ')'
 699
 700 # -------------------------------------------------- stack frame extraction
 701 def getframeinfo(frame, context=1):
 702     """Get information about a frame or traceback object.
 703
 704     A tuple of five things is returned: the filename, the line number of
 705     the current line, the function name, a list of lines of context from
 706     the source code, and the index of the current line within that list.
 707     The optional second argument specifies the number of lines of context
 708     to return, which are centered around the current line."""
 709     if istraceback(frame):
 710         frame = frame.tb_frame
 711     if not isframe(frame):
 712         raise TypeError, 'arg is not a frame or traceback object'
 713
 714     filename = getsourcefile(frame)
 715     lineno = getlineno(frame)
 716     if context > 0:
 717         start = lineno - 1 - context//2
 718         try:
 719             lines, lnum = findsource(frame)
 720         except IOError:
 721             lines = index = None
 722         else:
 723             start = max(start, 1)
 724             start = min(start, len(lines) - context)
 725             lines = lines[start:start+context]
 726             index = lineno - 1 - start
 727     else:
 728         lines = index = None
 729
 730     return (filename, lineno, frame.f_code.co_name, lines, index)
 731
 732 def getlineno(frame):
 733     """Get the line number from a frame object, allowing for optimization."""
 734     # Written by Marc-André Lemburg; revised by Jim Hugunin and Fredrik Lundh.
 735     lineno = frame.f_lineno
 736     code = frame.f_code
 737     if hasattr(code, 'co_lnotab'):
 738         table = code.co_lnotab
 739         lineno = code.co_firstlineno
 740         addr = 0
 741         for i in range(0, len(table), 2):
 742             addr = addr + ord(table[i])
 743             if addr > frame.f_lasti: break
 744             lineno = lineno + ord(table[i+1])
 745     return lineno
 746
 747 def getouterframes(frame, context=1):
 748     """Get a list of records for a frame and all higher (calling) frames.
 749
 750     Each record contains a frame object, filename, line number, function
 751     name, a list of lines of context, and index within the context."""
 752     framelist = []
 753     while frame:
 754         framelist.append((frame,) + getframeinfo(frame, context))
 755         frame = frame.f_back
 756     return framelist
 757
 758 def getinnerframes(tb, context=1):
 759     """Get a list of records for a traceback's frame and all lower frames.
 760
 761     Each record contains a frame object, filename, line number, function
 762     name, a list of lines of context, and index within the context."""
 763     framelist = []
 764     while tb:
 765         framelist.append((tb.tb_frame,) + getframeinfo(tb, context))
 766         tb = tb.tb_next
 767     return framelist
 768
 769 def currentframe():
 770     """Return the frame object for the caller's stack frame."""
 771     try:
 772         raise 'catch me'
 773     except:
 774         return sys.exc_traceback.tb_frame.f_back
 775
 776 if hasattr(sys, '_getframe'): currentframe = sys._getframe
 777
 778 def stack(context=1):
 779     """Return a list of records for the stack above the caller's frame."""
 780     return getouterframes(currentframe().f_back, context)
 781
 782 def trace(context=1):
 783     """Return a list of records for the stack below the current exception."""
 784     return getinnerframes(sys.exc_traceback, context)