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_tb(tb, 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 raise 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') 
193                  offset = min(len(caretspace), offset) - 1 
194                  caretspace = caretspace[:offset].lstrip() 
195                  # non-space whitespace (likes tabs) must be kept for alignment 
196                  caretspace = ((c.isspace() and c or ' ') for c in caretspace) 
197                  lines.append('    %s^\n' % ''.join(caretspace)) 
198          value = msg 
199   
200      lines.append(_format_final_exc_line(stype, value)) 
201      return lines 
202   
203 -def _format_final_exc_line(etype, value): 
204      """Return a list of a single line -- normal case for format_exception_only""" 
205      valuestr = _some_str(value) 
206      if value is None or not valuestr: 
207          line = "%s\n" % etype 
208      else: 
209          line = "%s: %s\n" % (etype, valuestr) 
210      return line 
211   
212 -def _some_str(value): 
213      try: 
214          return str(value) 
215      except Exception: 
216          pass 
217      try: 
218          value = unicode(value) 
219          return value.encode("ascii", "backslashreplace") 
220      except Exception: 
221          pass 
222      return '<unprintable %s object>' % type(value).__name__ 
223   
224   
225 -def print_exc(limit=None, file=None): 
226      """Shorthand for 'print_exception(sys.exc_type, sys.exc_value, sys.exc_traceback, limit, file)'. 
227      (In fact, it uses sys.exc_info() to retrieve the same information 
228      in a thread-safe way.)""" 
229      if file is None: 
230          file = sys.stderr 
231      try: 
232          etype, value, tb = sys.exc_info() 
233          print_exception(etype, value, tb, limit, file) 
234      finally: 
235          etype = value = tb = None 
236   
237   
238 -def format_exc(limit=None): 
239      """Like print_exc() but return a string.""" 
240      try: 
241          etype, value, tb = sys.exc_info() 
242          return ''.join(format_exception(etype, value, tb, limit)) 
243      finally: 
244          etype = value = tb = None 
245   
246   
247 -def print_last(limit=None, file=None): 
248      """This is a shorthand for 'print_exception(sys.last_type, 
249      sys.last_value, sys.last_traceback, limit, file)'.""" 
250      if not hasattr(sys, "last_type"): 
251          raise ValueError("no last exception") 
252      if file is None: 
253          file = sys.stderr 
254      print_exception(sys.last_type, sys.last_value, sys.last_traceback, 
255                      limit, file) 
256   
257   
258 -def print_stack(f=None, limit=None, file=None): 
259      """Print a stack trace from its invocation point. 
260   
261      The optional 'f' argument can be used to specify an alternate 
262      stack frame at which to start. The optional 'limit' and 'file' 
263      arguments have the same meaning as for print_exception(). 
264      """ 
265      if f is None: 
266          try: 
267              raise ZeroDivisionError 
268          except ZeroDivisionError: 
269              f = sys.exc_info()[2].tb_frame.f_back 
270      print_list(extract_stack(f, limit), file) 
271   
272 -def format_stack(f=None, limit=None): 
273      """Shorthand for 'format_list(extract_stack(f, limit))'.""" 
274      if f is None: 
275          try: 
276              raise ZeroDivisionError 
277          except ZeroDivisionError: 
278              f = sys.exc_info()[2].tb_frame.f_back 
279      return format_list(extract_stack(f, limit)) 
280   
281 -def extract_stack(f=None, limit = None): 
282      """Extract the raw traceback from the current stack frame. 
283   
284      The return value has the same format as for extract_tb().  The 
285      optional 'f' and 'limit' arguments have the same meaning as for 
286      print_stack().  Each item in the list is a quadruple (filename, 
287      line number, function name, text), and the entries are in order 
288      from oldest to newest stack frame. 
289      """ 
290      if f is None: 
291          try: 
292              raise ZeroDivisionError 
293          except ZeroDivisionError: 
294              f = sys.exc_info()[2].tb_frame.f_back 
295      if limit is None: 
296          if hasattr(sys, 'tracebacklimit'): 
297              limit = sys.tracebacklimit 
298      list = [] 
299      n = 0 
300      while f is not None and (limit is None or n < limit): 
301          lineno = f.f_lineno 
302          co = f.f_code 
303          filename = co.co_filename 
304          name = co.co_name 
305          linecache.checkcache(filename) 
306          line = linecache.getline(filename, lineno, f.f_globals) 
307          if line: line = line.strip() 
308          else: line = None 
309          list.append((filename, lineno, name, line)) 
310          f = f.f_back 
311          n = n+1 
312      list.reverse() 
313      return list 
314   
315 -def tb_lineno(tb): 
316      """Calculate correct line number of traceback given in tb. 
317   
318      Obsolete in 2.3. 
319      """ 
320      return tb.tb_lineno 
321