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/Lib/cmd.py

http://unladen-swallow.googlecode.com/
Python | 405 lines | 393 code | 4 blank | 8 comment | 12 complexity | 5203b52281ce65b240fab85c7bbdb663 MD5 | raw file
  1"""A generic class to build line-oriented command interpreters.
  2
  3Interpreters constructed with this class obey the following conventions:
  4
  51. End of file on input is processed as the command 'EOF'.
  62. A command is parsed out of each line by collecting the prefix composed
  7   of characters in the identchars member.
  83. A command `foo' is dispatched to a method 'do_foo()'; the do_ method
  9   is passed a single argument consisting of the remainder of the line.
 104. Typing an empty line repeats the last command.  (Actually, it calls the
 11   method `emptyline', which may be overridden in a subclass.)
 125. There is a predefined `help' method.  Given an argument `topic', it
 13   calls the command `help_topic'.  With no arguments, it lists all topics
 14   with defined help_ functions, broken into up to three topics; documented
 15   commands, miscellaneous help topics, and undocumented commands.
 166. The command '?' is a synonym for `help'.  The command '!' is a synonym
 17   for `shell', if a do_shell method exists.
 187. If completion is enabled, completing commands will be done automatically,
 19   and completing of commands args is done by calling complete_foo() with
 20   arguments text, line, begidx, endidx.  text is string we are matching
 21   against, all returned matches must begin with it.  line is the current
 22   input line (lstripped), begidx and endidx are the beginning and end
 23   indexes of the text being matched, which could be used to provide
 24   different completion depending upon which position the argument is in.
 25
 26The `default' method may be overridden to intercept commands for which there
 27is no do_ method.
 28
 29The `completedefault' method may be overridden to intercept completions for
 30commands that have no complete_ method.
 31
 32The data member `self.ruler' sets the character used to draw separator lines
 33in the help messages.  If empty, no ruler line is drawn.  It defaults to "=".
 34
 35If the value of `self.intro' is nonempty when the cmdloop method is called,
 36it is printed out on interpreter startup.  This value may be overridden
 37via an optional argument to the cmdloop() method.
 38
 39The data members `self.doc_header', `self.misc_header', and
 40`self.undoc_header' set the headers used for the help function's
 41listings of documented functions, miscellaneous topics, and undocumented
 42functions respectively.
 43
 44These interpreters use raw_input; thus, if the readline module is loaded,
 45they automatically support Emacs-like command history and editing features.
 46"""
 47
 48import string
 49
 50__all__ = ["Cmd"]
 51
 52PROMPT = '(Cmd) '
 53IDENTCHARS = string.ascii_letters + string.digits + '_'
 54
 55class Cmd:
 56    """A simple framework for writing line-oriented command interpreters.
 57
 58    These are often useful for test harnesses, administrative tools, and
 59    prototypes that will later be wrapped in a more sophisticated interface.
 60
 61    A Cmd instance or subclass instance is a line-oriented interpreter
 62    framework.  There is no good reason to instantiate Cmd itself; rather,
 63    it's useful as a superclass of an interpreter class you define yourself
 64    in order to inherit Cmd's methods and encapsulate action methods.
 65
 66    """
 67    prompt = PROMPT
 68    identchars = IDENTCHARS
 69    ruler = '='
 70    lastcmd = ''
 71    intro = None
 72    doc_leader = ""
 73    doc_header = "Documented commands (type help <topic>):"
 74    misc_header = "Miscellaneous help topics:"
 75    undoc_header = "Undocumented commands:"
 76    nohelp = "*** No help on %s"
 77    use_rawinput = 1
 78
 79    def __init__(self, completekey='tab', stdin=None, stdout=None):
 80        """Instantiate a line-oriented interpreter framework.
 81
 82        The optional argument 'completekey' is the readline name of a
 83        completion key; it defaults to the Tab key. If completekey is
 84        not None and the readline module is available, command completion
 85        is done automatically. The optional arguments stdin and stdout
 86        specify alternate input and output file objects; if not specified,
 87        sys.stdin and sys.stdout are used.
 88
 89        """
 90        import sys
 91        if stdin is not None:
 92            self.stdin = stdin
 93        else:
 94            self.stdin = sys.stdin
 95        if stdout is not None:
 96            self.stdout = stdout
 97        else:
 98            self.stdout = sys.stdout
 99        self.cmdqueue = []
100        self.completekey = completekey
101
102    def cmdloop(self, intro=None):
103        """Repeatedly issue a prompt, accept input, parse an initial prefix
104        off the received input, and dispatch to action methods, passing them
105        the remainder of the line as argument.
106
107        """
108
109        self.preloop()
110        if self.use_rawinput and self.completekey:
111            try:
112                import readline
113                self.old_completer = readline.get_completer()
114                readline.set_completer(self.complete)
115                readline.parse_and_bind(self.completekey+": complete")
116            except ImportError:
117                pass
118        try:
119            if intro is not None:
120                self.intro = intro
121            if self.intro:
122                self.stdout.write(str(self.intro)+"\n")
123            stop = None
124            while not stop:
125                if self.cmdqueue:
126                    line = self.cmdqueue.pop(0)
127                else:
128                    if self.use_rawinput:
129                        try:
130                            line = raw_input(self.prompt)
131                        except EOFError:
132                            line = 'EOF'
133                    else:
134                        self.stdout.write(self.prompt)
135                        self.stdout.flush()
136                        line = self.stdin.readline()
137                        if not len(line):
138                            line = 'EOF'
139                        else:
140                            line = line[:-1] # chop \n
141                line = self.precmd(line)
142                stop = self.onecmd(line)
143                stop = self.postcmd(stop, line)
144            self.postloop()
145        finally:
146            if self.use_rawinput and self.completekey:
147                try:
148                    import readline
149                    readline.set_completer(self.old_completer)
150                except ImportError:
151                    pass
152
153
154    def precmd(self, line):
155        """Hook method executed just before the command line is
156        interpreted, but after the input prompt is generated and issued.
157
158        """
159        return line
160
161    def postcmd(self, stop, line):
162        """Hook method executed just after a command dispatch is finished."""
163        return stop
164
165    def preloop(self):
166        """Hook method executed once when the cmdloop() method is called."""
167        pass
168
169    def postloop(self):
170        """Hook method executed once when the cmdloop() method is about to
171        return.
172
173        """
174        pass
175
176    def parseline(self, line):
177        """Parse the line into a command name and a string containing
178        the arguments.  Returns a tuple containing (command, args, line).
179        'command' and 'args' may be None if the line couldn't be parsed.
180        """
181        line = line.strip()
182        if not line:
183            return None, None, line
184        elif line[0] == '?':
185            line = 'help ' + line[1:]
186        elif line[0] == '!':
187            if hasattr(self, 'do_shell'):
188                line = 'shell ' + line[1:]
189            else:
190                return None, None, line
191        i, n = 0, len(line)
192        while i < n and line[i] in self.identchars: i = i+1
193        cmd, arg = line[:i], line[i:].strip()
194        return cmd, arg, line
195
196    def onecmd(self, line):
197        """Interpret the argument as though it had been typed in response
198        to the prompt.
199
200        This may be overridden, but should not normally need to be;
201        see the precmd() and postcmd() methods for useful execution hooks.
202        The return value is a flag indicating whether interpretation of
203        commands by the interpreter should stop.
204
205        """
206        cmd, arg, line = self.parseline(line)
207        if not line:
208            return self.emptyline()
209        if cmd is None:
210            return self.default(line)
211        self.lastcmd = line
212        if cmd == '':
213            return self.default(line)
214        else:
215            try:
216                func = getattr(self, 'do_' + cmd)
217            except AttributeError:
218                return self.default(line)
219            return func(arg)
220
221    def emptyline(self):
222        """Called when an empty line is entered in response to the prompt.
223
224        If this method is not overridden, it repeats the last nonempty
225        command entered.
226
227        """
228        if self.lastcmd:
229            return self.onecmd(self.lastcmd)
230
231    def default(self, line):
232        """Called on an input line when the command prefix is not recognized.
233
234        If this method is not overridden, it prints an error message and
235        returns.
236
237        """
238        self.stdout.write('*** Unknown syntax: %s\n'%line)
239
240    def completedefault(self, *ignored):
241        """Method called to complete an input line when no command-specific
242        complete_*() method is available.
243
244        By default, it returns an empty list.
245
246        """
247        return []
248
249    def completenames(self, text, *ignored):
250        dotext = 'do_'+text
251        return [a[3:] for a in self.get_names() if a.startswith(dotext)]
252
253    def complete(self, text, state):
254        """Return the next possible completion for 'text'.
255
256        If a command has not been entered, then complete against command list.
257        Otherwise try to call complete_<command> to get list of completions.
258        """
259        if state == 0:
260            import readline
261            origline = readline.get_line_buffer()
262            line = origline.lstrip()
263            stripped = len(origline) - len(line)
264            begidx = readline.get_begidx() - stripped
265            endidx = readline.get_endidx() - stripped
266            if begidx>0:
267                cmd, args, foo = self.parseline(line)
268                if cmd == '':
269                    compfunc = self.completedefault
270                else:
271                    try:
272                        compfunc = getattr(self, 'complete_' + cmd)
273                    except AttributeError:
274                        compfunc = self.completedefault
275            else:
276                compfunc = self.completenames
277            self.completion_matches = compfunc(text, line, begidx, endidx)
278        try:
279            return self.completion_matches[state]
280        except IndexError:
281            return None
282
283    def get_names(self):
284        # Inheritance says we have to look in class and
285        # base classes; order is not important.
286        names = []
287        classes = [self.__class__]
288        while classes:
289            aclass = classes.pop(0)
290            if aclass.__bases__:
291                classes = classes + list(aclass.__bases__)
292            names = names + dir(aclass)
293        return names
294
295    def complete_help(self, *args):
296        return self.completenames(*args)
297
298    def do_help(self, arg):
299        if arg:
300            # XXX check arg syntax
301            try:
302                func = getattr(self, 'help_' + arg)
303            except AttributeError:
304                try:
305                    doc=getattr(self, 'do_' + arg).__doc__
306                    if doc:
307                        self.stdout.write("%s\n"%str(doc))
308                        return
309                except AttributeError:
310                    pass
311                self.stdout.write("%s\n"%str(self.nohelp % (arg,)))
312                return
313            func()
314        else:
315            names = self.get_names()
316            cmds_doc = []
317            cmds_undoc = []
318            help = {}
319            for name in names:
320                if name[:5] == 'help_':
321                    help[name[5:]]=1
322            names.sort()
323            # There can be duplicates if routines overridden
324            prevname = ''
325            for name in names:
326                if name[:3] == 'do_':
327                    if name == prevname:
328                        continue
329                    prevname = name
330                    cmd=name[3:]
331                    if cmd in help:
332                        cmds_doc.append(cmd)
333                        del help[cmd]
334                    elif getattr(self, name).__doc__:
335                        cmds_doc.append(cmd)
336                    else:
337                        cmds_undoc.append(cmd)
338            self.stdout.write("%s\n"%str(self.doc_leader))
339            self.print_topics(self.doc_header,   cmds_doc,   15,80)
340            self.print_topics(self.misc_header,  help.keys(),15,80)
341            self.print_topics(self.undoc_header, cmds_undoc, 15,80)
342
343    def print_topics(self, header, cmds, cmdlen, maxcol):
344        if cmds:
345            self.stdout.write("%s\n"%str(header))
346            if self.ruler:
347                self.stdout.write("%s\n"%str(self.ruler * len(header)))
348            self.columnize(cmds, maxcol-1)
349            self.stdout.write("\n")
350
351    def columnize(self, list, displaywidth=80):
352        """Display a list of strings as a compact set of columns.
353
354        Each column is only as wide as necessary.
355        Columns are separated by two spaces (one was not legible enough).
356        """
357        if not list:
358            self.stdout.write("<empty>\n")
359            return
360        nonstrings = [i for i in range(len(list))
361                        if not isinstance(list[i], str)]
362        if nonstrings:
363            raise TypeError, ("list[i] not a string for i in %s" %
364                              ", ".join(map(str, nonstrings)))
365        size = len(list)
366        if size == 1:
367            self.stdout.write('%s\n'%str(list[0]))
368            return
369        # Try every row count from 1 upwards
370        for nrows in range(1, len(list)):
371            ncols = (size+nrows-1) // nrows
372            colwidths = []
373            totwidth = -2
374            for col in range(ncols):
375                colwidth = 0
376                for row in range(nrows):
377                    i = row + nrows*col
378                    if i >= size:
379                        break
380                    x = list[i]
381                    colwidth = max(colwidth, len(x))
382                colwidths.append(colwidth)
383                totwidth += colwidth + 2
384                if totwidth > displaywidth:
385                    break
386            if totwidth <= displaywidth:
387                break
388        else:
389            nrows = len(list)
390            ncols = 1
391            colwidths = [0]
392        for row in range(nrows):
393            texts = []
394            for col in range(ncols):
395                i = row + nrows*col
396                if i >= size:
397                    x = ""
398                else:
399                    x = list[i]
400                texts.append(x)
401            while texts and not texts[-1]:
402                del texts[-1]
403            for col in range(len(texts)):
404                texts[col] = texts[col].ljust(colwidths[col])
405            self.stdout.write("%s\n"%str("  ".join(texts)))