Source Code for Module mvpa.misc.io.hamster

  1  #emacs: -*- mode: python-mode; py-indent-offset: 4; indent-tabs-mode: nil -*- 
  2  #ex: set sts=4 ts=4 sw=4 et: 
  3  ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ## 
  4  # 
  5  #   See COPYING file distributed along with the PyMVPA package for the 
  6  #   copyright and license terms. 
  7  # 
  8  ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ## 
  9  """Helper for simple storage facility via cPickle and zlib""" 
 10   
 11  __docformat__ = 'restructuredtext' 
 12   
 13  import os 
 14   
 15  from mvpa.base import externals 
 16  externals.exists('cPickle', raiseException=True) 
 17  externals.exists('gzip', raiseException=True) 
 18   
 19  _d_geti_ = dict.__getitem__ 
 20  _d_seti_ = dict.__setitem__ 
 21   
 22  _o_geta_ = dict.__getattribute__ 
 23  _o_seta_ = dict.__setattr__ 
 24   
 25  import cPickle, gzip 
 26   
 27  if __debug__: 
 28      from mvpa.base import debug 
 29   
 30 -class Hamster(object): 
 31      """Simple container class with basic IO capabilities. 
 32   
 33      It is capable of storing itself in a file, or loading from a file 
 34      (using cPickle + zlib tandem). Any serializable object can be 
 35      bound to a hamster to be stored. 
 36   
 37      To undig burried hamster use Hamster(filename). Here is an example: 
 38   
 39        >>> h = Hamster(bla='blai') 
 40        >>> h.boo = N.arange(5) 
 41        >>> h.dump(filename) 
 42        ... 
 43        >>> h = Hamster(filename) 
 44   
 45      Since Hamster introduces methods `dump`, `asdict` and property 
 46      'registered', those names cannot be used to assign an attribute, 
 47      nor provided in among constructor arguments. 
 48      """ 
 49   
 50      __ro_attr = set(object.__dict__.keys() + 
 51                      ['dump', 'registered', 'asdict']) 
 52      """Attributes which come with being an object""" 
 53   
 54 -    def __new__(cls, *args, **kwargs): 
 55          if len(args) > 0: 
 56              if len(kwargs) > 0: 
 57                  raise ValueError, \ 
 58                        "Do not mix positional and keyword arguments. " \ 
 59                        "Use a single positional argument -- filename, " \ 
 60                        "or any number of keyword arguments, without having " \ 
 61                        "filename specified" 
 62              if len(args) == 1 and isinstance(args[0], basestring): 
 63                  filename = args[0] 
 64                  args = args[1:] 
 65                  if __debug__: 
 66                      debug('IOH', 'Undigging hamster from %s' % filename) 
 67                  f = gzip.open(filename) 
 68                  result = cPickle.load(f) 
 69                  if not isinstance(result, Hamster): 
 70                      warning("Loaded other than Hamster class from %s" % filename) 
 71                  return result 
 72              else: 
 73                  raise ValueError, "Hamster accepts only a single positional " \ 
 74                        "argument and it must be a filename. Got %d " \ 
 75                        "arguments" % (len(args),) 
 76          else: 
 77              return object.__new__(cls) 
 78   
 79   
 80 -    def __init__(self, *args, **kwargs): 
 81          """Initialize Hamster. 
 82   
 83          Providing a single parameter string would treat it as a 
 84          filename from which to undig the data. Otherwise all keyword 
 85          parameters are assigned into the attributes of the object. 
 86          """ 
 87          if len(args) > 0: 
 88              if len(args) == 1 and isinstance(args[0], basestring): 
 89                  # it was a filename 
 90                  args = args[1:] 
 91              else: 
 92                  raise RuntimeError, "Should not get here" 
 93   
 94          # assign provided attributes 
 95          for k,v in kwargs.iteritems(): 
 96              setattr(self, k, v) 
 97   
 98          object.__init__(self) 
 99   
100   
101 -    def dump(self, filename): 
102          """Bury the hamster into the file 
103          """ 
104          if __debug__: 
105              debug('IOH', 'Burying hamster into %s' % filename) 
106          f = gzip.open(filename, 'w') 
107          cPickle.dump(self, f) 
108          f.close() 
109   
110   
111 -    def __repr__(self): 
112          reg_attr = ["%s=%s" % (k, repr(getattr(self, k))) 
113                      for k in self.registered] 
114          return "%s(%s)" % (self.__class__.__name__, 
115                             ", ".join(reg_attr)) 
116   
117      # ??? actually seems to be ugly 
118      #def __str__(self): 
119      #    registered = self.registered 
120      #    return "%s with %d elements: %s" \ 
121      #           % (self.__class__.__name__, 
122      #              len(registered), 
123      #              ", ".join(self.registered)) 
124   
125      @property 
126 -    def registered(self): 
127          """List registered attributes. 
128          """ 
129          reg_attr = [k for k in self.__dict__.iterkeys() 
130                      if not k in self.__ro_attr] 
131          reg_attr.sort() 
132          return reg_attr 
133   
134   
135 -    def __setattr__(self, k, v): 
136          """Just to prevent resetting read-only attributes, such as methods 
137          """ 
138          if k in self.__ro_attr: 
139              raise ValueError, "'%s' object attribute '%s' is read-only" \ 
140                    % (self.__class__.__name__, k) 
141          object.__setattr__(self, k, v) 
142   
143   
144 -    def asdict(self): 
145          """Return registered data as dictionary 
146          """ 
147          return dict([(k, getattr(self, k)) 
148                       for k in self.registered]) 
149