Source Code for Module dns.exception

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 15   
 16  """Common DNS Exceptions.""" 
 17   
 18   
 19 -class DNSException(Exception): 
 20   
 21      """Abstract base class shared by all dnspython exceptions. 
 22   
 23      It supports two basic modes of operation: 
 24   
 25      a) Old/compatible mode is used if __init__ was called with 
 26         empty **kwargs. 
 27      In compatible mode all *args are passed to standard Python Exception class 
 28      as before and all *args are printed by standard __str__ implementation. 
 29      Class variable msg (or doc string if msg is None) is returned from str() 
 30      if *args is empty. 
 31   
 32      b) New/parametrized mode is used if __init__ was called with 
 33         non-empty **kwargs. 
 34      In the new mode *args has to be empty and all kwargs has to exactly match 
 35      set in class variable self.supp_kwargs. All kwargs are stored inside 
 36      self.kwargs and used in new __str__ implementation to construct 
 37      formatted message based on self.fmt string. 
 38   
 39      In the simplest case it is enough to override supp_kwargs and fmt 
 40      class variables to get nice parametrized messages. 
 41      """ 
 42      msg = None  # non-parametrized message 
 43      supp_kwargs = set()  # accepted parameters for _fmt_kwargs (sanity check) 
 44      fmt = None  # message parametrized with results from _fmt_kwargs 
 45   
 46 -    def __init__(self, *args, **kwargs): 
 47          self._check_params(*args, **kwargs) 
 48          self._check_kwargs(**kwargs) 
 49          self.kwargs = kwargs 
 50          if self.msg is None: 
 51              # doc string is better implicit message than empty string 
 52              self.msg = self.__doc__ 
 53          if args: 
 54              super(DNSException, self).__init__(*args) 
 55          else: 
 56              super(DNSException, self).__init__(self.msg) 
 57   
 58 -    def _check_params(self, *args, **kwargs): 
 59          """Old exceptions supported only args and not kwargs. 
 60   
 61          For sanity we do not allow to mix old and new behavior.""" 
 62          if args or kwargs: 
 63              assert bool(args) != bool(kwargs), \ 
 64                  'keyword arguments are mutually exclusive with positional args' 
 65   
 66 -    def _check_kwargs(self, **kwargs): 
 67          if kwargs: 
 68              assert set(kwargs.keys()) == self.supp_kwargs, \ 
 69                  'following set of keyword args is required: %s' % ( 
 70                      self.supp_kwargs) 
 71   
 72 -    def _fmt_kwargs(self, **kwargs): 
 73          """Format kwargs before printing them. 
 74   
 75          Resulting dictionary has to have keys necessary for str.format call 
 76          on fmt class variable. 
 77          """ 
 78          fmtargs = {} 
 79          for kw, data in kwargs.items(): 
 80              if isinstance(data, (list, set)): 
 81                  # convert list of <someobj> to list of str(<someobj>) 
 82                  fmtargs[kw] = list(map(str, data)) 
 83                  if len(fmtargs[kw]) == 1: 
 84                      # remove list brackets [] from single-item lists 
 85                      fmtargs[kw] = fmtargs[kw].pop() 
 86              else: 
 87                  fmtargs[kw] = data 
 88          return fmtargs 
 89   
 90 -    def __str__(self): 
 91          if self.kwargs and self.fmt: 
 92              # provide custom message constructed from keyword arguments 
 93              fmtargs = self._fmt_kwargs(**self.kwargs) 
 94              return self.fmt.format(**fmtargs) 
 95          else: 
 96              # print *args directly in the same way as old DNSException 
 97              return super(DNSException, self).__str__() 
 98   
 99   
100 -class FormError(DNSException): 
101   
102      """DNS message is malformed.""" 
103   
104   
105 -class SyntaxError(DNSException): 
106   
107      """Text input is malformed.""" 
108   
109   
110 -class UnexpectedEnd(SyntaxError): 
111   
112      """Text input ended unexpectedly.""" 
113   
114   
115 -class TooBig(DNSException): 
116   
117      """The DNS message is too big.""" 
118   
119   
120 -class Timeout(DNSException): 
121   
122      """The DNS operation timed out.""" 
123      supp_kwargs = set(['timeout']) 
124      fmt = "The DNS operation timed out after {timeout} seconds" 
125