Source Code for Module traceback

  1  """Extract, format and print information about Python stack traces.""" 
  2   
  3  import linecache 
  4  import sys 
  5  import types 
  6   
  7  __all__ = ['extract_stack', 'extract_tb', 'format_exception', 
  8             'format_exception_only', 'format_list', 'format_stack', 
  9             'format_tb', 'print_exc', 'format_exc', 'print_exception', 
 10             'print_last', 'print_stack', 'print_tb', 'tb_lineno'] 
 11   
 12 -def _print(file, str='', terminator='\n'): 
 13      file.write(str+terminator) 
 14   
 15   
 16 -def print_list(extracted_list, file=None): 
 17      """Print the list of tuples as returned by extract_tb() or 
 18      extract_stack() as a formatted stack trace to the given file.""" 
 19      if file is None: 
 20          file = sys.stderr 
 21      for filename, lineno, name, line in extracted_list: 
 22          _print(file, 
 23                 '  File "%s", line %d, in %s' % (filename,lineno,name)) 
 24          if line: 
 25              _print(file, '    %s' % line.strip()) 
 26   
 27 -def format_list(extracted_list): 
 28      """Format a list of traceback entry tuples for printing. 
 29   
 30      Given a list of tuples as returned by extract_tb() or 
 31      extract_stack(), return a list of strings ready for printing. 
 32      Each string in the resulting list corresponds to the item with the 
 33      same index in the argument list.  Each string ends in a newline; 
 34      the strings may contain internal newlines as well, for those items 
 35      whose source text line is not None. 
 36      """ 
 37      list = [] 
 38      for filename, lineno, name, line in extracted_list: 
 39          item = '  File "%s", line %d, in %s\n' % (filename,lineno,name) 
 40          if line: 
 41              item = item + '    %s\n' % line.strip() 
 42          list.append(item) 
 43      return list 
 44   
 45   
 46 -def print_tb(tb, limit=None, file=None): 
 47      """Print up to 'limit' stack trace entries from the traceback 'tb'. 
 48   
 49      If 'limit' is omitted or None, all entries are printed.  If 'file' 
 50      is omitted or None, the output goes to sys.stderr; otherwise 
 51      'file' should be an open file or file-like object with a write() 
 52      method. 
 53      """ 
 54      if file is None: 
 55          file = sys.stderr 
 56      if limit is None: 
 57          if hasattr(sys, 'tracebacklimit'): 
 58              limit = sys.tracebacklimit 
 59      n = 0 
 60      while tb is not None and (limit is None or n < limit): 
 61          f = tb.tb_frame 
 62          lineno = tb.tb_lineno 
 63          co = f.f_code 
 64          filename = co.co_filename 
 65          name = co.co_name 
 66          _print(file, 
 67                 '  File "%s", line %d, in %s' % (filename, lineno, name)) 
 68          linecache.checkcache(filename) 
 69          line = linecache.getline(filename, lineno, f.f_globals) 
 70          if line: _print(file, '    ' + line.strip()) 
 71          tb = tb.tb_next 
 72          n = n+1 
 73   
 74 -def format_tb(tb, limit = None): 
 75      """A shorthand for 'format_list(extract_stack(f, limit)).""" 
 76      return format_list(extract_tb(tb, limit)) 
 77   
 78 -def extract_tb(tb, limit = None): 
 79      """Return list of up to limit pre-processed entries from traceback. 
 80   
 81      This is useful for alternate formatting of stack traces.  If 
 82      'limit' is omitted or None, all entries are extracted.  A 
 83      pre-processed stack trace entry is a quadruple (filename, line 
 84      number, function name, text) representing the information that is 
 85      usually printed for a stack trace.  The text is a string with 
 86      leading and trailing whitespace stripped; if the source is not 
 87      available it is None. 
 88      """ 
 89      if limit is None: 
 90          if hasattr(sys, 'tracebacklimit'): 
 91              limit = sys.tracebacklimit 
 92      list = [] 
 93      n = 0 
 94      while tb is not None and (limit is None or n < limit): 
 95          f = tb.tb_frame 
 96          lineno = tb.tb_lineno 
 97          co = f.f_code 
 98          filename = co.co_filename 
 99          name = co.co_name 
100          linecache.checkcache(filename) 
101          line = linecache.getline(filename, lineno, f.f_globals) 
102          if line: line = line.strip() 
103          else: line = None 
104          list.append((filename, lineno, name, line)) 
105          tb = tb.tb_next 
106          n = n+1 
107      return list 
108   
109   
110 -def print_exception(etype, value, tb, limit=None, file=None): 
111      """Print exception up to 'limit' stack trace entries from 'tb' to 'file'. 
112   
113      This differs from print_tb() in the following ways: (1) if 
114      traceback is not None, it prints a header "Traceback (most recent 
115      call last):"; (2) it prints the exception type and value after the 
116      stack trace; (3) if type is SyntaxError and value has the 
117      appropriate format, it prints the line where the syntax error 
118      occurred with a caret on the next line indicating the approximate 
119      position of the error. 
120      """ 
121      if file is None: 
122          file = sys.stderr 
123      if tb: 
124          _print(file, 'Traceback (most recent call last):') 
125          print_tb(tb, limit, file) 
126      lines = format_exception_only(etype, value) 
127      for line in lines: 
128          _print(file, line, '') 
129   
130 -def format_exception(etype, value, tb, limit = None): 
131      """Format a stack trace and the exception information. 
132   
133      The arguments have the same meaning as the corresponding arguments 
134      to print_exception().  The return value is a list of strings, each 
135      ending in a newline and some containing internal newlines.  When 
136      these lines are concatenated and printed, exactly the same text is 
137      printed as does print_exception(). 
138      """ 
139      if tb: 
140          list = ['Traceback (most recent call last):\n'] 
141          list = list + format_tb(tb, limit) 
142      else: 
143          list = [] 
144      list = list + format_exception_only(etype, value) 
145      return list 
146   
147 -def format_exception_only(etype, value): 
148      """Format the exception part of a traceback. 
149   
150      The arguments are the exception type and value such as given by 
151      sys.last_type and sys.last_value. The return value is a list of 
152      strings, each ending in a newline. 
153   
154      Normally, the list contains a single string; however, for 
155      SyntaxError exceptions, it contains several lines that (when 
156      printed) display detailed information about where the syntax 
157      error occurred. 
158   
159      The message indicating which exception occurred is always the last 
160      string in the list. 
161   
162      """ 
163   
164      # An instance should not have a meaningful value parameter, but 
165      # sometimes does, particularly for string exceptions, such as 
166      # >>> raise string1, string2  # deprecated 
167      # 
168      # Clear these out first because issubtype(string1, SyntaxError) 
169      # would throw another exception and mask the original problem. 
170      if (isinstance(etype, BaseException) or 
171          isinstance(etype, types.InstanceType) or 
172          etype is None or type(etype) is str): 
173          return [_format_final_exc_line(etype, value)] 
174   
175      stype = etype.__name__ 
176   
177      if not issubclass(etype, SyntaxError): 
178          return [_format_final_exc_line(stype, value)] 
179   
180      # It was a syntax error; show exactly where the problem was found. 
181      lines = [] 
182      try: 
183          msg, (filename, lineno, offset, badline) = value.args 
184      except Exception: 
185          pass 
186      else: 
187          filename = filename or "<string>" 
188          lines.append('  File "%s", line %d\n' % (filename, lineno)) 
189          if badline is not None: 
190              lines.append('    %s\n' % badline.strip()) 
191              if offset is not None: 
192                  caretspace = badline.rstrip('\n')[:offset].lstrip() 
193                  # non-space whitespace (likes tabs) must be kept for alignment 
194                  caretspace = ((c.isspace() and c or ' ') for c in caretspace) 
195                  # only three spaces to account for offset1 == pos 0 
196                  lines.append('   %s^\n' % ''.join(caretspace)) 
197          value = msg 
198   
199      lines.append(_format_final_exc_line(stype, value)) 
200      return lines 
201   
202 -def _format_final_exc_line(etype, value): 
203      """Return a list of a single line -- normal case for format_exception_only""" 
204      valuestr = _some_str(value) 
205      if value is None or not valuestr: 
206          line = "%s\n" % etype 
207      else: 
208          line = "%s: %s\n" % (etype, valuestr) 
209      return line 
210   
211 -def _some_str(value): 
212      try: 
213          return str(value) 
214      except Exception: 
215          pass 
216      try: 
217          value = unicode(value) 
218          return value.encode("ascii", "backslashreplace") 
219      except Exception: 
220          pass 
221      return '<unprintable %s object>' % type(value).__name__ 
222   
223   
224 -def print_exc(limit=None, file=None): 
225      """Shorthand for 'print_exception(sys.exc_type, sys.exc_value, sys.exc_traceback, limit, file)'. 
226      (In fact, it uses sys.exc_info() to retrieve the same information 
227      in a thread-safe way.)""" 
228      if file is None: 
229          file = sys.stderr 
230      try: 
231          etype, value, tb = sys.exc_info() 
232          print_exception(etype, value, tb, limit, file) 
233      finally: 
234          etype = value = tb = None 
235   
236   
237 -def format_exc(limit=None): 
238      """Like print_exc() but return a string.""" 
239      try: 
240          etype, value, tb = sys.exc_info() 
241          return ''.join(format_exception(etype, value, tb, limit)) 
242      finally: 
243          etype = value = tb = None 
244   
245   
246 -def print_last(limit=None, file=None): 
247      """This is a shorthand for 'print_exception(sys.last_type, 
248      sys.last_value, sys.last_traceback, limit, file)'.""" 
249      if not hasattr(sys, "last_type"): 
250          raise ValueError("no last exception") 
251      if file is None: 
252          file = sys.stderr 
253      print_exception(sys.last_type, sys.last_value, sys.last_traceback, 
254                      limit, file) 
255   
256   
257 -def print_stack(f=None, limit=None, file=None): 
258      """Print a stack trace from its invocation point. 
259   
260      The optional 'f' argument can be used to specify an alternate 
261      stack frame at which to start. The optional 'limit' and 'file' 
262      arguments have the same meaning as for print_exception(). 
263      """ 
264      if f is None: 
265          try: 
266              raise ZeroDivisionError 
267          except ZeroDivisionError: 
268              f = sys.exc_info()[2].tb_frame.f_back 
269      print_list(extract_stack(f, limit), file) 
270   
271 -def format_stack(f=None, limit=None): 
272      """Shorthand for 'format_list(extract_stack(f, limit))'.""" 
273      if f is None: 
274          try: 
275              raise ZeroDivisionError 
276          except ZeroDivisionError: 
277              f = sys.exc_info()[2].tb_frame.f_back 
278      return format_list(extract_stack(f, limit)) 
279   
280 -def extract_stack(f=None, limit = None): 
281      """Extract the raw traceback from the current stack frame. 
282   
283      The return value has the same format as for extract_tb().  The 
284      optional 'f' and 'limit' arguments have the same meaning as for 
285      print_stack().  Each item in the list is a quadruple (filename, 
286      line number, function name, text), and the entries are in order 
287      from oldest to newest stack frame. 
288      """ 
289      if f is None: 
290          try: 
291              raise ZeroDivisionError 
292          except ZeroDivisionError: 
293              f = sys.exc_info()[2].tb_frame.f_back 
294      if limit is None: 
295          if hasattr(sys, 'tracebacklimit'): 
296              limit = sys.tracebacklimit 
297      list = [] 
298      n = 0 
299      while f is not None and (limit is None or n < limit): 
300          lineno = f.f_lineno 
301          co = f.f_code 
302          filename = co.co_filename 
303          name = co.co_name 
304          linecache.checkcache(filename) 
305          line = linecache.getline(filename, lineno, f.f_globals) 
306          if line: line = line.strip() 
307          else: line = None 
308          list.append((filename, lineno, name, line)) 
309          f = f.f_back 
310          n = n+1 
311      list.reverse() 
312      return list 
313   
314 -def tb_lineno(tb): 
315      """Calculate correct line number of traceback given in tb. 
316   
317      Obsolete in 2.3. 
318      """ 
319      return tb.tb_lineno 
320