Ka-Ping Yee | 6397c7c | 2001-02-27 14:43:21 +0000 | [diff] [blame] | 1 | \section{\module{inspect} --- |
| 2 | Inspect live objects} |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 3 | |
Ka-Ping Yee | 6397c7c | 2001-02-27 14:43:21 +0000 | [diff] [blame] | 4 | \declaremodule{standard}{inspect} |
| 5 | \modulesynopsis{Extract information and source code from live objects.} |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 6 | \moduleauthor{Ka-Ping Yee}{ping@lfw.org} |
| 7 | \sectionauthor{Ka-Ping Yee}{ping@lfw.org} |
Ka-Ping Yee | 6397c7c | 2001-02-27 14:43:21 +0000 | [diff] [blame] | 8 | |
| 9 | \versionadded{2.1} |
| 10 | |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 11 | The \module{inspect} module provides several useful functions |
Ka-Ping Yee | 6397c7c | 2001-02-27 14:43:21 +0000 | [diff] [blame] | 12 | to help get information about live objects such as modules, |
| 13 | classes, methods, functions, tracebacks, frame objects, and |
| 14 | code objects. For example, it can help you examine the |
| 15 | contents of a class, retrieve the source code of a method, |
| 16 | extract and format the argument list for a function, or |
| 17 | get all the information you need to display a detailed traceback. |
| 18 | |
| 19 | There are four main kinds of services provided by this module: |
| 20 | type checking, getting source code, inspecting classes |
| 21 | and functions, and examining the interpreter stack. |
| 22 | |
| 23 | \subsection{Types and members |
| 24 | \label{inspect-types}} |
| 25 | |
| 26 | The \function{getmembers()} function retrieves the members |
| 27 | of an object such as a class or module. |
| 28 | The nine functions whose names begin with ``is'' are mainly |
| 29 | provided as convenient choices for the second argument to |
| 30 | \function{getmembers()}. They also help you determine when |
| 31 | you can expect to find the following special attributes: |
| 32 | |
Fred Drake | f9d5803 | 2001-12-07 23:13:53 +0000 | [diff] [blame] | 33 | \begin{tableiv}{c|l|l|c}{}{Type}{Attribute}{Description}{Notes} |
| 34 | \lineiv{module}{__doc__}{documentation string}{} |
| 35 | \lineiv{}{__file__}{filename (missing for built-in modules)}{} |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 36 | \hline |
Fred Drake | f9d5803 | 2001-12-07 23:13:53 +0000 | [diff] [blame] | 37 | \lineiv{class}{__doc__}{documentation string}{} |
| 38 | \lineiv{}{__module__}{name of module in which this class was defined}{} |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 39 | \hline |
Fred Drake | f9d5803 | 2001-12-07 23:13:53 +0000 | [diff] [blame] | 40 | \lineiv{method}{__doc__}{documentation string}{} |
| 41 | \lineiv{}{__name__}{name with which this method was defined}{} |
| 42 | \lineiv{}{im_class}{class object that asked for this method}{(1)} |
| 43 | \lineiv{}{im_func}{function object containing implementation of method}{} |
| 44 | \lineiv{}{im_self}{instance to which this method is bound, or \code{None}}{} |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 45 | \hline |
Fred Drake | f9d5803 | 2001-12-07 23:13:53 +0000 | [diff] [blame] | 46 | \lineiv{function}{__doc__}{documentation string}{} |
| 47 | \lineiv{}{__name__}{name with which this function was defined}{} |
| 48 | \lineiv{}{func_code}{code object containing compiled function bytecode}{} |
| 49 | \lineiv{}{func_defaults}{tuple of any default values for arguments}{} |
| 50 | \lineiv{}{func_doc}{(same as __doc__)}{} |
| 51 | \lineiv{}{func_globals}{global namespace in which this function was defined}{} |
| 52 | \lineiv{}{func_name}{(same as __name__)}{} |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 53 | \hline |
Fred Drake | f9d5803 | 2001-12-07 23:13:53 +0000 | [diff] [blame] | 54 | \lineiv{traceback}{tb_frame}{frame object at this level}{} |
| 55 | \lineiv{}{tb_lasti}{index of last attempted instruction in bytecode}{} |
| 56 | \lineiv{}{tb_lineno}{current line number in Python source code}{} |
| 57 | \lineiv{}{tb_next}{next inner traceback object (called by this level)}{} |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 58 | \hline |
Fred Drake | f9d5803 | 2001-12-07 23:13:53 +0000 | [diff] [blame] | 59 | \lineiv{frame}{f_back}{next outer frame object (this frame's caller)}{} |
| 60 | \lineiv{}{f_builtins}{built-in namespace seen by this frame}{} |
| 61 | \lineiv{}{f_code}{code object being executed in this frame}{} |
| 62 | \lineiv{}{f_exc_traceback}{traceback if raised in this frame, or \code{None}}{} |
| 63 | \lineiv{}{f_exc_type}{exception type if raised in this frame, or \code{None}}{} |
| 64 | \lineiv{}{f_exc_value}{exception value if raised in this frame, or \code{None}}{} |
| 65 | \lineiv{}{f_globals}{global namespace seen by this frame}{} |
| 66 | \lineiv{}{f_lasti}{index of last attempted instruction in bytecode}{} |
| 67 | \lineiv{}{f_lineno}{current line number in Python source code}{} |
| 68 | \lineiv{}{f_locals}{local namespace seen by this frame}{} |
| 69 | \lineiv{}{f_restricted}{0 or 1 if frame is in restricted execution mode}{} |
| 70 | \lineiv{}{f_trace}{tracing function for this frame, or \code{None}}{} |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 71 | \hline |
Fred Drake | f9d5803 | 2001-12-07 23:13:53 +0000 | [diff] [blame] | 72 | \lineiv{code}{co_argcount}{number of arguments (not including * or ** args)}{} |
| 73 | \lineiv{}{co_code}{string of raw compiled bytecode}{} |
| 74 | \lineiv{}{co_consts}{tuple of constants used in the bytecode}{} |
| 75 | \lineiv{}{co_filename}{name of file in which this code object was created}{} |
| 76 | \lineiv{}{co_firstlineno}{number of first line in Python source code}{} |
| 77 | \lineiv{}{co_flags}{bitmap: 1=optimized \code{|} 2=newlocals \code{|} 4=*arg \code{|} 8=**arg}{} |
| 78 | \lineiv{}{co_lnotab}{encoded mapping of line numbers to bytecode indices}{} |
| 79 | \lineiv{}{co_name}{name with which this code object was defined}{} |
| 80 | \lineiv{}{co_names}{tuple of names of local variables}{} |
| 81 | \lineiv{}{co_nlocals}{number of local variables}{} |
| 82 | \lineiv{}{co_stacksize}{virtual machine stack space required}{} |
| 83 | \lineiv{}{co_varnames}{tuple of names of arguments and local variables}{} |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 84 | \hline |
Fred Drake | f9d5803 | 2001-12-07 23:13:53 +0000 | [diff] [blame] | 85 | \lineiv{builtin}{__doc__}{documentation string}{} |
| 86 | \lineiv{}{__name__}{original name of this function or method}{} |
| 87 | \lineiv{}{__self__}{instance to which a method is bound, or \code{None}}{} |
| 88 | \end{tableiv} |
| 89 | |
| 90 | \noindent |
| 91 | Note: |
| 92 | \begin{description} |
| 93 | \item[(1)] |
| 94 | \versionchanged[\member{im_class} used to refer to the class that |
| 95 | defined the method]{2.2} |
| 96 | \end{description} |
| 97 | |
Ka-Ping Yee | 6397c7c | 2001-02-27 14:43:21 +0000 | [diff] [blame] | 98 | |
| 99 | \begin{funcdesc}{getmembers}{object\optional{, predicate}} |
| 100 | Return all the members of an object in a list of (name, value) pairs |
| 101 | sorted by name. If the optional \var{predicate} argument is supplied, |
| 102 | only members for which the predicate returns a true value are included. |
| 103 | \end{funcdesc} |
| 104 | |
Fred Drake | 90a72f8 | 2001-04-10 15:12:34 +0000 | [diff] [blame] | 105 | \begin{funcdesc}{getmoduleinfo}{path} |
| 106 | Return a tuple of values that describe how Python will interpret the |
| 107 | file identified by \var{path} if it is a module, or \code{None} if |
| 108 | it would not be identified as a module. The return tuple is |
| 109 | \code{(\var{name}, \var{suffix}, \var{mode}, \var{mtype})}, where |
| 110 | \var{name} is the name of the module without the name of any |
| 111 | enclosing package, \var{suffix} is the trailing part of the file |
| 112 | name (which may not be a dot-delimited extension), \var{mode} is the |
| 113 | \function{open()} mode that would be used (\code{'r'} or |
| 114 | \code{'rb'}), and \var{mtype} is an integer giving the type of the |
| 115 | module. \var{mtype} will have a value which can be compared to the |
| 116 | constants defined in the \refmodule{imp} module; see the |
| 117 | documentation for that module for more information on module types. |
| 118 | \end{funcdesc} |
| 119 | |
| 120 | \begin{funcdesc}{getmodulename}{path} |
| 121 | Return the name of the module named by the file \var{path}, without |
| 122 | including the names of enclosing packages. This uses the same |
| 123 | algortihm as the interpreter uses when searching for modules. If |
| 124 | the name cannot be matched according to the interpreter's rules, |
| 125 | \code{None} is returned. |
| 126 | \end{funcdesc} |
| 127 | |
Ka-Ping Yee | 6397c7c | 2001-02-27 14:43:21 +0000 | [diff] [blame] | 128 | \begin{funcdesc}{ismodule}{object} |
| 129 | Return true if the object is a module. |
| 130 | \end{funcdesc} |
| 131 | |
| 132 | \begin{funcdesc}{isclass}{object} |
| 133 | Return true if the object is a class. |
| 134 | \end{funcdesc} |
| 135 | |
| 136 | \begin{funcdesc}{ismethod}{object} |
| 137 | Return true if the object is a method. |
| 138 | \end{funcdesc} |
| 139 | |
| 140 | \begin{funcdesc}{isfunction}{object} |
| 141 | Return true if the object is a Python function or unnamed (lambda) function. |
| 142 | \end{funcdesc} |
| 143 | |
| 144 | \begin{funcdesc}{istraceback}{object} |
| 145 | Return true if the object is a traceback. |
| 146 | \end{funcdesc} |
| 147 | |
| 148 | \begin{funcdesc}{isframe}{object} |
| 149 | Return true if the object is a frame. |
| 150 | \end{funcdesc} |
| 151 | |
| 152 | \begin{funcdesc}{iscode}{object} |
| 153 | Return true if the object is a code. |
| 154 | \end{funcdesc} |
| 155 | |
| 156 | \begin{funcdesc}{isbuiltin}{object} |
| 157 | Return true if the object is a built-in function. |
| 158 | \end{funcdesc} |
| 159 | |
| 160 | \begin{funcdesc}{isroutine}{object} |
| 161 | Return true if the object is a user-defined or built-in function or method. |
| 162 | \end{funcdesc} |
| 163 | |
| 164 | \subsection{Retrieving source code |
| 165 | \label{inspect-source}} |
| 166 | |
| 167 | \begin{funcdesc}{getdoc}{object} |
| 168 | Get the documentation string for an object. |
| 169 | All tabs are expanded to spaces. To clean up docstrings that are |
| 170 | indented to line up with blocks of code, any whitespace than can be |
| 171 | uniformly removed from the second line onwards is removed. |
| 172 | \end{funcdesc} |
| 173 | |
| 174 | \begin{funcdesc}{getcomments}{object} |
| 175 | Return in a single string any lines of comments immediately preceding |
| 176 | the object's source code (for a class, function, or method), or at the |
| 177 | top of the Python source file (if the object is a module). |
| 178 | \end{funcdesc} |
| 179 | |
| 180 | \begin{funcdesc}{getfile}{object} |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 181 | Return the name of the (text or binary) file in which an object was |
| 182 | defined. This will fail with a \exception{TypeError} if the object |
| 183 | is a built-in module, class, or function. |
Ka-Ping Yee | 6397c7c | 2001-02-27 14:43:21 +0000 | [diff] [blame] | 184 | \end{funcdesc} |
| 185 | |
| 186 | \begin{funcdesc}{getmodule}{object} |
| 187 | Try to guess which module an object was defined in. |
| 188 | \end{funcdesc} |
| 189 | |
| 190 | \begin{funcdesc}{getsourcefile}{object} |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 191 | Return the name of the Python source file in which an object was |
| 192 | defined. This will fail with a \exception{TypeError} if the object |
| 193 | is a built-in module, class, or function. |
Ka-Ping Yee | 6397c7c | 2001-02-27 14:43:21 +0000 | [diff] [blame] | 194 | \end{funcdesc} |
| 195 | |
| 196 | \begin{funcdesc}{getsourcelines}{object} |
| 197 | Return a list of source lines and starting line number for an object. |
| 198 | The argument may be a module, class, method, function, traceback, frame, |
| 199 | or code object. The source code is returned as a list of the lines |
| 200 | corresponding to the object and the line number indicates where in the |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 201 | original source file the first line of code was found. An |
| 202 | \exception{IOError} is raised if the source code cannot be retrieved. |
Ka-Ping Yee | 6397c7c | 2001-02-27 14:43:21 +0000 | [diff] [blame] | 203 | \end{funcdesc} |
| 204 | |
| 205 | \begin{funcdesc}{getsource}{object} |
| 206 | Return the text of the source code for an object. |
| 207 | The argument may be a module, class, method, function, traceback, frame, |
| 208 | or code object. The source code is returned as a single string. An |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 209 | \exception{IOError} is raised if the source code cannot be retrieved. |
Ka-Ping Yee | 6397c7c | 2001-02-27 14:43:21 +0000 | [diff] [blame] | 210 | \end{funcdesc} |
| 211 | |
| 212 | \subsection{Classes and functions |
| 213 | \label{inspect-classes-functions}} |
| 214 | |
| 215 | \begin{funcdesc}{getclasstree}{classes\optional{, unique}} |
| 216 | Arrange the given list of classes into a hierarchy of nested lists. |
| 217 | Where a nested list appears, it contains classes derived from the class |
| 218 | whose entry immediately precedes the list. Each entry is a 2-tuple |
| 219 | containing a class and a tuple of its base classes. If the \var{unique} |
| 220 | argument is true, exactly one entry appears in the returned structure |
| 221 | for each class in the given list. Otherwise, classes using multiple |
| 222 | inheritance and their descendants will appear multiple times. |
| 223 | \end{funcdesc} |
| 224 | |
| 225 | \begin{funcdesc}{getargspec}{func} |
| 226 | Get the names and default values of a function's arguments. |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 227 | A tuple of four things is returned: \code{(\var{args}, |
| 228 | \var{varargs}, \var{varkw}, \var{defaults})}. |
Ka-Ping Yee | 6397c7c | 2001-02-27 14:43:21 +0000 | [diff] [blame] | 229 | \var{args} is a list of the argument names (it may contain nested lists). |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 230 | \var{varargs} and \var{varkw} are the names of the \code{*} and |
| 231 | \code{**} arguments or \code{None}. |
Ka-Ping Yee | 6397c7c | 2001-02-27 14:43:21 +0000 | [diff] [blame] | 232 | \var{defaults} is a tuple of default argument values; if this tuple |
| 233 | has \var{n} elements, they correspond to the last \var{n} elements |
| 234 | listed in \var{args}. |
| 235 | \end{funcdesc} |
| 236 | |
| 237 | \begin{funcdesc}{getargvalues}{frame} |
| 238 | Get information about arguments passed into a particular frame. |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 239 | A tuple of four things is returned: \code{(\var{args}, |
| 240 | \var{varargs}, \var{varkw}, \var{locals})}. |
| 241 | \var{args} is a list of the argument names (it may contain nested |
| 242 | lists). |
| 243 | \var{varargs} and \var{varkw} are the names of the \code{*} and |
| 244 | \code{**} arguments or \code{None}. |
Ka-Ping Yee | 6397c7c | 2001-02-27 14:43:21 +0000 | [diff] [blame] | 245 | \var{locals} is the locals dictionary of the given frame. |
| 246 | \end{funcdesc} |
| 247 | |
| 248 | \begin{funcdesc}{formatargspec}{args\optional{, varargs, varkw, defaults, |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 249 | argformat, varargsformat, varkwformat, defaultformat}} |
Tim Peters | e0b2d7a | 2001-09-22 06:10:55 +0000 | [diff] [blame] | 250 | |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 251 | Format a pretty argument spec from the four values returned by |
| 252 | \function{getargspec()}. The other four arguments are the |
| 253 | corresponding optional formatting functions that are called to turn |
| 254 | names and values into strings. |
Ka-Ping Yee | 6397c7c | 2001-02-27 14:43:21 +0000 | [diff] [blame] | 255 | \end{funcdesc} |
| 256 | |
| 257 | \begin{funcdesc}{formatargvalues}{args\optional{, varargs, varkw, locals, |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 258 | argformat, varargsformat, varkwformat, valueformat}} |
| 259 | Format a pretty argument spec from the four values returned by |
| 260 | \function{getargvalues()}. The other four arguments are the |
| 261 | corresponding optional formatting functions that are called to turn |
| 262 | names and values into strings. |
Ka-Ping Yee | 6397c7c | 2001-02-27 14:43:21 +0000 | [diff] [blame] | 263 | \end{funcdesc} |
| 264 | |
Tim Peters | e0b2d7a | 2001-09-22 06:10:55 +0000 | [diff] [blame] | 265 | \begin{funcdesc}{getmro}{cls} |
| 266 | Return a tuple of class cls's base classes, including cls, in |
| 267 | method resolution order. No class appears more than once in this tuple. |
| 268 | Note that the method resolution order depends on cls's type. Unless a |
| 269 | very peculiar user-defined metatype is in use, cls will be the first |
| 270 | element of the tuple. |
| 271 | \end{funcdesc} |
| 272 | |
Ka-Ping Yee | 6397c7c | 2001-02-27 14:43:21 +0000 | [diff] [blame] | 273 | \subsection{The interpreter stack |
| 274 | \label{inspect-stack}} |
| 275 | |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 276 | When the following functions return ``frame records,'' each record |
Ka-Ping Yee | 6397c7c | 2001-02-27 14:43:21 +0000 | [diff] [blame] | 277 | is a tuple of six items: the frame object, the filename, |
| 278 | the line number of the current line, the function name, a list of |
| 279 | lines of context from the source code, and the index of the current |
| 280 | line within that list. |
| 281 | The optional \var{context} argument specifies the number of lines of |
| 282 | context to return, which are centered around the current line. |
| 283 | |
Fred Drake | 0aa811c | 2001-10-20 04:24:09 +0000 | [diff] [blame] | 284 | \warning{Keeping references to frame objects, as found in |
Fred Drake | d635e3c | 2001-08-10 17:37:33 +0000 | [diff] [blame] | 285 | the first element of the frame records these functions return, can |
| 286 | cause your program to create reference cycles. Once a reference cycle |
| 287 | has been created, the lifespan of all objects which can be accessed |
| 288 | from the objects which form the cycle can become much longer even if |
| 289 | Python's optional cycle detector is enabled. If such cycles must be |
| 290 | created, it is important to ensure they are explicitly broken to avoid |
| 291 | the delayed destruction of objects and increased memory consumption |
Fred Drake | 0aa811c | 2001-10-20 04:24:09 +0000 | [diff] [blame] | 292 | which occurs.} |
Fred Drake | d635e3c | 2001-08-10 17:37:33 +0000 | [diff] [blame] | 293 | |
Tim Peters | 61acf06 | 2001-10-16 23:01:06 +0000 | [diff] [blame] | 294 | \begin{funcdesc}{getframeinfo}{frame\optional{, context}} |
| 295 | Get information about a frame or traceback object. A 5-tuple |
| 296 | is returned, the last five elements of the frame's frame record. |
| 297 | The optional second argument specifies the number of lines of context |
| 298 | to return, which are centered around the current line. |
Fred Drake | ca836f7 | 2001-10-18 14:26:08 +0000 | [diff] [blame] | 299 | \end{funcdesc} |
Tim Peters | 61acf06 | 2001-10-16 23:01:06 +0000 | [diff] [blame] | 300 | |
Ka-Ping Yee | 6397c7c | 2001-02-27 14:43:21 +0000 | [diff] [blame] | 301 | \begin{funcdesc}{getouterframes}{frame\optional{, context}} |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 302 | Get a list of frame records for a frame and all higher (calling) |
| 303 | frames. |
Ka-Ping Yee | 6397c7c | 2001-02-27 14:43:21 +0000 | [diff] [blame] | 304 | \end{funcdesc} |
| 305 | |
| 306 | \begin{funcdesc}{getinnerframes}{traceback\optional{, context}} |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 307 | Get a list of frame records for a traceback's frame and all lower |
| 308 | frames. |
Ka-Ping Yee | 6397c7c | 2001-02-27 14:43:21 +0000 | [diff] [blame] | 309 | \end{funcdesc} |
| 310 | |
| 311 | \begin{funcdesc}{currentframe}{} |
| 312 | Return the frame object for the caller's stack frame. |
| 313 | \end{funcdesc} |
| 314 | |
| 315 | \begin{funcdesc}{stack}{\optional{context}} |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 316 | Return a list of frame records for the stack above the caller's |
| 317 | frame. |
Ka-Ping Yee | 6397c7c | 2001-02-27 14:43:21 +0000 | [diff] [blame] | 318 | \end{funcdesc} |
| 319 | |
| 320 | \begin{funcdesc}{trace}{\optional{context}} |
Fred Drake | 6dbd382 | 2001-02-28 23:01:38 +0000 | [diff] [blame] | 321 | Return a list of frame records for the stack below the current |
| 322 | exception. |
Ka-Ping Yee | 6397c7c | 2001-02-27 14:43:21 +0000 | [diff] [blame] | 323 | \end{funcdesc} |