Source Code for Module dns.exception

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