inspect: a module for getting information out of live Python objects

1 files changed, 616 insertions, 0 deletions

diff --git a/Lib/inspect.py b/Lib/inspect.py
new file mode 100644
index 0000000..408e454
--- /dev/null
+++ b/Lib/inspect.py
@@ -0,0 +1,616 @@
+"""Get useful information from live Python objects.
+
+This module encapsulates the interface provided by the internal special
+attributes (func_*, co_*, im_*, tb_*, etc.) in a friendlier fashion.
+It also provides some help for examining source code and class layout.
+
+Here are some of the useful functions provided by this module:
+
+    ismodule(), isclass(), ismethod(), isfunction(), istraceback(),
+        isframe(), iscode(), isbuiltin(), isroutine() - check object types
+    getmembers() - get members of an object that satisfy a given condition
+
+    getfile(), getsourcefile(), getsource() - find an object's source code
+    getdoc(), getcomments() - get documentation on an object
+    getmodule() - determine the module that an object came from
+    getclasstree() - arrange classes so as to represent their hierarchy
+
+    getargspec(), getargvalues() - get info about function arguments
+    formatargspec(), formatargvalues() - format an argument spec
+    getouterframes(), getinnerframes() - get info about frames
+    currentframe() - get the current stack frame
+    stack(), trace() - get info about frames on the stack or in a traceback
+"""
+
+# This module is in the public domain.  No warranties.
+
+__version__ = 'Ka-Ping Yee <ping@lfw.org>, 1 Jan 2001'
+
+import sys, types, string, dis, imp, tokenize
+
+# ----------------------------------------------------------- type-checking
+def ismodule(object):
+    """Return true if the object is a module.
+
+    Module objects provide these attributes:
+        __doc__         documentation string
+        __file__        filename (missing for built-in modules)"""
+    return type(object) is types.ModuleType
+
+def isclass(object):
+    """Return true if the object is a class.
+
+    Class objects provide these attributes:
+        __doc__         documentation string
+        __module__      name of module in which this class was defined"""
+    return type(object) is types.ClassType
+
+def ismethod(object):
+    """Return true if the object is an instance method.
+
+    Instance method objects provide these attributes:
+        __doc__         documentation string
+        __name__        name with which this method was defined
+        im_class        class object in which this method belongs
+        im_func         function object containing implementation of method
+        im_self         instance to which this method is bound, or None"""
+    return type(object) is types.MethodType
+
+def isfunction(object):
+    """Return true if the object is a user-defined function.
+
+    Function objects provide these attributes:
+        __doc__         documentation string
+        __name__        name with which this function was defined
+        func_code       code object containing compiled function bytecode
+        func_defaults   tuple of any default values for arguments
+        func_doc        (same as __doc__)
+        func_globals    global namespace in which this function was defined
+        func_name       (same as __name__)"""
+    return type(object) in [types.FunctionType, types.LambdaType]
+
+def istraceback(object):
+    """Return true if the object is a traceback.
+
+    Traceback objects provide these attributes:
+        tb_frame        frame object at this level
+        tb_lasti        index of last attempted instruction in bytecode
+        tb_lineno       current line number in Python source code
+        tb_next         next inner traceback object (called by this level)"""
+    return type(object) is types.TracebackType
+
+def isframe(object):
+    """Return true if the object is a frame object.
+
+    Frame objects provide these attributes:
+        f_back          next outer frame object (this frame's caller)
+        f_builtins      built-in namespace seen by this frame
+        f_code          code object being executed in this frame
+        f_exc_traceback traceback if raised in this frame, or None
+        f_exc_type      exception type if raised in this frame, or None
+        f_exc_value     exception value if raised in this frame, or None
+        f_globals       global namespace seen by this frame
+        f_lasti         index of last attempted instruction in bytecode
+        f_lineno        current line number in Python source code
+        f_locals        local namespace seen by this frame
+        f_restricted    0 or 1 if frame is in restricted execution mode
+        f_trace         tracing function for this frame, or None"""
+    return type(object) is types.FrameType
+
+def iscode(object):
+    """Return true if the object is a code object.
+
+    Code objects provide these attributes:
+        co_argcount     number of arguments (not including * or ** args)
+        co_code         string of raw compiled bytecode
+        co_consts       tuple of constants used in the bytecode
+        co_filename     name of file in which this code object was created
+        co_firstlineno  number of first line in Python source code
+        co_flags        bitmap: 1=optimized | 2=newlocals | 4=*arg | 8=**arg
+        co_lnotab       encoded mapping of line numbers to bytecode indices
+        co_name         name with which this code object was defined
+        co_names        tuple of names of local variables
+        co_nlocals      number of local variables
+        co_stacksize    virtual machine stack space required
+        co_varnames     tuple of names of arguments and local variables"""
+    return type(object) is types.CodeType
+
+def isbuiltin(object):
+    """Return true if the object is a built-in function or method.
+
+    Built-in functions and methods provide these attributes:
+        __doc__         documentation string
+        __name__        original name of this function or method
+        __self__        instance to which a method is bound, or None"""
+    return type(object) in [types.BuiltinFunctionType,
+                            types.BuiltinMethodType]
+
+def isroutine(object):
+    """Return true if the object is any kind of function or method."""
+    return type(object) in [types.FunctionType, types.LambdaType,
+                            types.MethodType, types.BuiltinFunctionType,
+                            types.BuiltinMethodType]
+
+def getmembers(object, predicate=None):
+    """Return all members of an object as (name, value) pairs sorted by name.
+    Optionally, only return members that satisfy a given predicate."""
+    results = []
+    for key in dir(object):
+        value = getattr(object, key)
+        if not predicate or predicate(value):
+            results.append((key, value))
+    results.sort()
+    return results
+
+# -------------------------------------------------- source code extraction
+def indentsize(line):
+    """Return the indent size, in spaces, at the start of a line of text."""
+    expline = string.expandtabs(line)
+    return len(expline) - len(string.lstrip(expline))
+
+def getdoc(object):
+    """Get the documentation string for an object.
+
+    All tabs are expanded to spaces.  To clean up docstrings that are
+    indented to line up with blocks of code, any whitespace than can be
+    uniformly removed from the second line onwards is removed."""
+    if hasattr(object, '__doc__') and object.__doc__:
+        lines = string.split(string.expandtabs(object.__doc__), '\n')
+        margin = None
+        for line in lines[1:]:
+            content = len(string.lstrip(line))
+            if not content: continue
+            indent = len(line) - content
+            if margin is None: margin = indent
+            else: margin = min(margin, indent)
+        if margin is not None:
+            for i in range(1, len(lines)): lines[i] = lines[i][margin:]
+        return string.join(lines, '\n')
+
+def getfile(object):
+    """Try to guess which (text or binary) file an object was defined in."""
+    if ismodule(object):
+        if hasattr(object, '__file__'):
+            return object.__file__
+        raise TypeError, 'arg is a built-in module'
+    if isclass(object):
+        object = sys.modules[object.__module__]
+        if hasattr(object, '__file__'):
+            return object.__file__
+        raise TypeError, 'arg is a built-in class'
+    if ismethod(object):
+        object = object.im_func
+    if isfunction(object):
+        object = object.func_code
+    if istraceback(object):
+        object = object.tb_frame
+    if isframe(object):
+        object = object.f_code
+    if iscode(object):
+        return object.co_filename
+    raise TypeError, 'arg is not a module, class, method, ' \
+                     'function, traceback, frame, or code object'
+
+modulesbyfile = {}
+
+def getmodule(object):
+    """Try to guess which module an object was defined in."""
+    if isclass(object):
+        return sys.modules[object.__module__]
+    try:
+        file = getsourcefile(object)
+    except TypeError:
+        return None
+    if modulesbyfile.has_key(file):
+        return sys.modules[modulesbyfile[file]]
+    for module in sys.modules.values():
+        if hasattr(module, '__file__'):
+            modulesbyfile[getsourcefile(module)] = module.__name__
+    if modulesbyfile.has_key(file):
+        return sys.modules[modulesbyfile[file]]
+    main = sys.modules['__main__']
+    try:
+        mainobject = getattr(main, object.__name__)
+        if mainobject is object: return main
+    except AttributeError: pass
+    builtin = sys.modules['__builtin__']
+    try:
+        builtinobject = getattr(builtin, object.__name__)
+        if builtinobject is object: return builtin
+    except AttributeError: pass
+
+def getsourcefile(object):
+    """Try to guess which Python source file an object was defined in."""
+    filename = getfile(object)
+    if filename[-4:] == '.pyc':
+        filename = filename[:-4] + '.py'
+    return filename
+
+def findsource(object):
+    """Return the entire source file and starting line number for an object.
+
+    The argument may be a module, class, method, function, traceback, frame,
+    or code object.  The source code is returned as a list of all the lines
+    in the file and the line number indexes a line in that list.  An IOError
+    is raised if the source code cannot be retrieved."""
+    try:
+        file = open(getsourcefile(object))
+        lines = file.readlines()
+        file.close()
+    except (TypeError, IOError):
+        raise IOError, 'could not get source code'
+
+    if ismodule(object):
+        return lines, 0
+
+    if isclass(object):
+        name = object.__name__
+        matches = (['class', name], ['class', name + ':'])
+        for i in range(len(lines)):
+            if string.split(lines[i])[:2] in matches:
+                return lines, i
+        else: raise IOError, 'could not find class definition'
+
+    if ismethod(object):
+        object = object.im_func
+    if isfunction(object):
+        object = object.func_code
+    if istraceback(object):
+        object = object.tb_frame
+    if isframe(object):
+        object = object.f_code
+    if iscode(object):
+        try:
+            lnum = object.co_firstlineno - 1
+        except AttributeError:
+            raise IOError, 'could not find function definition'
+        else:
+            while lnum > 0:
+                if string.split(lines[lnum])[:1] == ['def']: break
+                lnum = lnum - 1
+            return lines, lnum
+
+def getcomments(object):
+    """Get lines of comments immediately preceding an object's source code."""
+    try: lines, lnum = findsource(object)
+    except: return None
+
+    if ismodule(object):
+        # Look for a comment block at the top of the file.
+        start = 0
+        if lines[0][:2] == '#!': start = 1
+        while start < len(lines) and string.strip(lines[start]) in ['', '#']:
+            start = start + 1
+        if lines[start][:1] == '#':
+            comments = []
+            end = start
+            while end < len(lines) and lines[end][:1] == '#':
+                comments.append(string.expandtabs(lines[end]))
+                end = end + 1
+            return string.join(comments, '')
+
+    # Look for a preceding block of comments at the same indentation.
+    elif lnum > 0:
+        indent = indentsize(lines[lnum])
+        end = lnum - 1
+        if end >= 0 and string.lstrip(lines[end])[:1] == '#' and \
+            indentsize(lines[end]) == indent:
+            comments = [string.lstrip(string.expandtabs(lines[end]))]
+            if end > 0:
+                end = end - 1
+                comment = string.lstrip(string.expandtabs(lines[end]))
+                while comment[:1] == '#' and indentsize(lines[end]) == indent:
+                    comments[:0] = [comment]
+                    end = end - 1
+                    if end < 0: break
+                    comment = string.lstrip(string.expandtabs(lines[end]))
+            while comments and string.strip(comments[0]) == '#':
+                comments[:1] = []
+            while comments and string.strip(comments[-1]) == '#':
+                comments[-1:] = []
+            return string.join(comments, '')
+
+class ListReader:
+    """Provide a readline() method to return lines from a list of strings."""
+    def __init__(self, lines):
+        self.lines = lines
+        self.index = 0
+
+    def readline(self):
+        i = self.index
+        if i < len(self.lines):
+            self.index = i + 1
+            return self.lines[i]
+        else: return ''
+
+class EndOfBlock(Exception): pass
+
+class BlockFinder:
+    """Provide a tokeneater() method to detect the end of a code block."""
+    def __init__(self):
+        self.indent = 0
+        self.started = 0
+        self.last = 0
+
+    def tokeneater(self, type, token, (srow, scol), (erow, ecol), line):
+        if not self.started:
+            if type == tokenize.NAME: self.started = 1
+        elif type == tokenize.NEWLINE:
+            self.last = srow
+        elif type == tokenize.INDENT:
+            self.indent = self.indent + 1
+        elif type == tokenize.DEDENT:
+            self.indent = self.indent - 1
+            if self.indent == 0: raise EndOfBlock, self.last
+
+def getblock(lines):
+    """Extract the block of code at the top of the given list of lines."""
+    try:
+        tokenize.tokenize(ListReader(lines).readline, BlockFinder().tokeneater)
+    except EndOfBlock, eob:
+        return lines[:eob.args[0]]
+
+def getsourcelines(object):
+    """Return a list of source lines and starting line number for an object.
+
+    The argument may be a module, class, method, function, traceback, frame,
+    or code object.  The source code is returned as a list of the lines
+    corresponding to the object and the line number indicates where in the
+    original source file the first line of code was found.  An IOError is
+    raised if the source code cannot be retrieved."""
+    lines, lnum = findsource(object)
+
+    if ismodule(object): return lines, 0
+    else: return getblock(lines[lnum:]), lnum + 1
+
+def getsource(object):
+    """Return the text of the source code for an object.
+
+    The argument may be a module, class, method, function, traceback, frame,
+    or code object.  The source code is returned as a single string.  An
+    IOError is raised if the source code cannot be retrieved."""
+    lines, lnum = getsourcelines(object)
+    return string.join(lines, '')
+
+# --------------------------------------------------- class tree extraction
+def walktree(classes, children, parent):
+    """Recursive helper function for getclasstree()."""
+    results = []
+    classes.sort(lambda a, b: cmp(a.__name__, b.__name__))
+    for c in classes:
+        results.append((c, c.__bases__))
+        if children.has_key(c):
+            results.append(walktree(children[c], children, c))
+    return results
+
+def getclasstree(classes, unique=0):
+    """Arrange the given list of classes into a hierarchy of nested lists.
+
+    Where a nested list appears, it contains classes derived from the class
+    whose entry immediately precedes the list.  Each entry is a 2-tuple
+    containing a class and a tuple of its base classes.  If the 'unique'
+    argument is true, exactly one entry appears in the returned structure
+    for each class in the given list.  Otherwise, classes using multiple
+    inheritance and their descendants will appear multiple times."""
+    children = {}
+    roots = []
+    for c in classes:
+        if c.__bases__:
+            for parent in c.__bases__:
+                if not children.has_key(parent):
+                    children[parent] = []
+                children[parent].append(c)
+                if unique and parent in classes: break
+        elif c not in roots:
+            roots.append(c)
+    for parent in children.keys():
+        if parent not in classes:
+            roots.append(parent)
+    return walktree(roots, children, None)
+
+# ------------------------------------------------ argument list extraction
+# These constants are from Python's compile.h.
+CO_OPTIMIZED, CO_NEWLOCALS, CO_VARARGS, CO_VARKEYWORDS = 1, 2, 4, 8
+
+def getargs(co):
+    """Get information about the arguments accepted by a code object.
+
+    Three things are returned: (args, varargs, varkw), where 'args' is
+    a list of argument names (possibly containing nested lists), and
+    'varargs' and 'varkw' are the names of the * and ** arguments or None."""
+    if not iscode(co): raise TypeError, 'arg is not a code object'
+
+    code = co.co_code
+    nargs = co.co_argcount
+    names = co.co_varnames
+    args = list(names[:nargs])
+    step = 0
+
+    # The following acrobatics are for anonymous (tuple) arguments.
+    for i in range(nargs):
+        if args[i][:1] in ['', '.']:
+            stack, remain, count = [], [], []
+            while step < len(code):
+                op = ord(code[step])
+                step = step + 1
+                if op >= dis.HAVE_ARGUMENT:
+                    opname = dis.opname[op]
+                    value = ord(code[step]) + ord(code[step+1])*256
+                    step = step + 2
+                    if opname in ['UNPACK_TUPLE', 'UNPACK_SEQUENCE']:
+                        remain.append(value)
+                        count.append(value)
+                    elif opname == 'STORE_FAST':
+                        stack.append(names[value])
+                        remain[-1] = remain[-1] - 1
+                        while remain[-1] == 0:
+                            remain.pop()
+                            size = count.pop()
+                            stack[-size:] = [stack[-size:]]
+                            if not remain: break
+                            remain[-1] = remain[-1] - 1
+                        if not remain: break
+            args[i] = stack[0]
+
+    varargs = None
+    if co.co_flags & CO_VARARGS:
+        varargs = co.co_varnames[nargs]
+        nargs = nargs + 1
+    varkw = None
+    if co.co_flags & CO_VARKEYWORDS:
+        varkw = co.co_varnames[nargs]
+    return args, varargs, varkw
+
+def getargspec(func):
+    """Get the names and default values of a function's arguments.
+
+    A tuple of four things is returned: (args, varargs, varkw, defaults).
+    'args' is a list of the argument names (it may contain nested lists).
+    'varargs' and 'varkw' are the names of the * and ** arguments or None.
+    'defaults' is an n-tuple of the default values of the last n arguments."""
+    if not isfunction(func): raise TypeError, 'arg is not a Python function'
+    args, varargs, varkw = getargs(func.func_code)
+    return args, varargs, varkw, func.func_defaults
+
+def getargvalues(frame):
+    """Get information about arguments passed into a particular frame.
+
+    A tuple of four things is returned: (args, varargs, varkw, locals).
+    'args' is a list of the argument names (it may contain nested lists).
+    'varargs' and 'varkw' are the names of the * and ** arguments or None.
+    'locals' is the locals dictionary of the given frame."""
+    args, varargs, varkw = getargs(frame.f_code)
+    return args, varargs, varkw, frame.f_locals
+
+def joinseq(seq):
+    if len(seq) == 1:
+        return '(' + seq[0] + ',)'
+    else:
+        return '(' + string.join(seq, ', ') + ')'
+
+def strseq(object, convert, join=joinseq):
+    """Recursively walk a sequence, stringifying each element."""
+    if type(object) in [types.ListType, types.TupleType]:
+        return join(map(lambda o, c=convert, j=join: strseq(o, c, j), object))
+    else:
+        return convert(object)
+
+def formatargspec(args, varargs=None, varkw=None, defaults=None,
+                  formatarg=str,
+                  formatvarargs=lambda name: '*' + name,
+                  formatvarkw=lambda name: '**' + name,
+                  formatvalue=lambda value: '=' + repr(value),
+                  join=joinseq):
+    """Format an argument spec from the 4 values returned by getargspec.
+
+    The first four arguments are (args, varargs, varkw, defaults).  The
+    other four arguments are the corresponding optional formatting functions
+    that are called to turn names and values into strings.  The ninth
+    argument is an optional function to format the sequence of arguments."""
+    specs = []
+    if defaults:
+        firstdefault = len(args) - len(defaults)
+    for i in range(len(args)):
+        spec = strseq(args[i], formatarg, join)
+        if defaults and i >= firstdefault:
+            spec = spec + formatvalue(defaults[i - firstdefault])
+        specs.append(spec)
+    if varargs:
+        specs.append(formatvarargs(varargs))
+    if varkw:
+        specs.append(formatvarkw(varkw))
+    return '(' + string.join(specs, ', ') + ')'
+
+def formatargvalues(args, varargs, varkw, locals,
+                    formatarg=str,
+                    formatvarargs=lambda name: '*' + name,
+                    formatvarkw=lambda name: '**' + name,
+                    formatvalue=lambda value: '=' + repr(value),
+                    join=joinseq):
+    """Format an argument spec from the 4 values returned by getargvalues.
+
+    The first four arguments are (args, varargs, varkw, locals).  The
+    next four arguments are the corresponding optional formatting functions
+    that are called to turn names and values into strings.  The ninth
+    argument is an optional function to format the sequence of arguments."""
+    def convert(name, locals=locals,
+                formatarg=formatarg, formatvalue=formatvalue):
+        return formatarg(name) + formatvalue(locals[name])
+    specs = []
+    for i in range(len(args)):
+        specs.append(strseq(args[i], convert, join))
+    if varargs:
+        specs.append(formatvarargs(varargs) + formatvalue(locals[varargs]))
+    if varkw:
+        specs.append(formatvarkw(varkw) + formatvalue(locals[varkw]))
+    return '(' + string.join(specs, ', ') + ')'
+
+# -------------------------------------------------- stack frame extraction
+def getframeinfo(frame, context=1):
+    """Get information about a frame or traceback object.
+
+    A tuple of five things is returned: the filename, the line number of
+    the current line, the function name, a list of lines of context from
+    the source code, and the index of the current line within that list.
+    The optional second argument specifies the number of lines of context
+    to return, which are centered around the current line."""
+    if istraceback(frame):
+        frame = frame.tb_frame
+    if not isframe(frame):
+        raise TypeError, 'arg is not a frame or traceback object'
+
+    filename = getsourcefile(frame)
+    if context > 0:
+        start = frame.f_lineno - 1 - context/2
+        try:
+            lines, lnum = findsource(frame)
+            start = max(start, 1)
+            start = min(start, len(lines) - context)
+            lines = lines[start:start+context]
+            index = frame.f_lineno - 1 - start
+        except:
+            lines = index = None
+    else:
+        lines = index = None
+
+    return (filename, frame.f_lineno, frame.f_code.co_name, lines, index)
+
+def getouterframes(frame, context=1):
+    """Get a list of records for a frame and all higher (calling) frames.
+
+    Each record contains a frame object, filename, line number, function
+    name, a list of lines of context, and index within the context."""
+    framelist = []
+    while frame:
+        framelist.append((frame,) + getframeinfo(frame, context))
+        frame = frame.f_back
+    return framelist
+
+def getinnerframes(tb, context=1):
+    """Get a list of records for a traceback's frame and all lower frames.
+
+    Each record contains a frame object, filename, line number, function
+    name, a list of lines of context, and index within the context."""
+    tb = tb.tb_next
+    framelist = []
+    while tb:
+        framelist.append((tb.tb_frame,) + getframeinfo(tb, context))
+        tb = tb.tb_next
+    return framelist
+
+def currentframe():
+    """Return the frame object for the caller's stack frame."""
+    try:
+        raise 'catch me'
+    except:
+        return sys.exc_traceback.tb_frame.f_back
+
+if hasattr(sys, '_getframe'): currentframe = sys._getframe
+
+def stack(context=1):
+    """Return a list of records for the stack above the caller's frame."""
+    return getouterframes(currentframe().f_back, context)
+
+def trace(context=1):
+    """Return a list of records for the stack below the current exception.""" 
+    return getinnerframes(sys.exc_traceback, context)