Source Code for Module osh.command.expand

  1  # osh 
  2  # Copyright (C) Jack Orenstein <jao@geophile.com> 
  3  # 
  4  # This program is free software; you can redistribute it and/or modify 
  5  # it under the terms of the GNU General Public License as published by 
  6  # the Free Software Foundation; either version 2 of the License, or 
  7  # (at your option) any later version. 
  8  # 
  9  # This program is distributed in the hope that it will be useful, 
 10  # but WITHOUT ANY WARRANTY; without even the implied warranty of 
 11  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
 12  # GNU General Public License for more details. 
 13  # 
 14  # You should have received a copy of the GNU General Public License 
 15  # along with this program; if not, write to the Free Software 
 16  # Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 
 17   
 18  """C{expand [POSITION]} 
 19   
 20  Receives a stream of sequences as input. If C{POSITION} is omitted, then 
 21  each item of the sequence is generated as a separate 1-tuple in the 
 22  output stream. 
 23   
 24  B{Example}: If the input contains these sequences:: 
 25   
 26      ('a', 'b') 
 27      ('c', 'd') 
 28   
 29  then C{expand} generates this output:: 
 30      ('a',) 
 31      ('b',) 
 32      ('c',) 
 33      ('d',) 
 34   
 35  If C{POSITION} is specified, then each input sequence is used to generate 
 36  zero or more output sequences. In each output sequence, the item at the 
 37  selected position is replaced by one component of the selected object. 
 38   
 39  The types that can be expanded are C{list}, C{tuple}, C{generator}, 
 40  and C{osh.file.File}. Expansion of a C{osh.file.File} 
 41  yields each line of the named file. 
 42   
 43  B{Example}: If the input contains these sequences:: 
 44   
 45      ('a', [1, 2, 3], 'x') 
 46      ('b', [4, 5], 'y') 
 47      ('c', [], 'z') 
 48   
 49  then C{expand 1} generates this output:: 
 50   
 51      ('a', 1, 'x') 
 52      ('a', 2, 'x') 
 53      ('a', 3, 'x') 
 54      ('b', 4, 'y') 
 55      ('b', 5, 'y') 
 56   
 57  Note that an empty nested sequence results in no output, (as for 
 58  C{('c', [], 'z')}.) 
 59  """ 
 60   
 61  import types 
 62   
 63  import osh.core 
 64  import osh.file 
 65   
 66  # CLI 
 67 -def _expand(): 
 68      return _Expand() 
 69   
 70  # API 
 71 -def expand(position = None): 
 72      """Flattens an input sequence by generating output sequences in which an interior element 
 73      is expanded. If C{position} is omitted, then each element of the input sequence is generated 
 74      as a separate 1-tuples. If C{position} is specified, then the item at the given position 
 75      is expanded. If the element being expanded is a string, then the string is interpreted 
 76      as a filename, and the expansion yields each line of the file in turn. 
 77      """ 
 78      args = [] 
 79      if position is not None: 
 80          args.append(position) 
 81      return _Expand().process_args(*args) 
 82   
 83 -class _Expand(osh.core.Op): 
 84   
 85      _expander = None 
 86   
 87   
 88      # object interface 
 89   
 90 -    def __init__(self): 
 91          osh.core.Op.__init__(self, None, (0, 1)) 
 92       
 93   
 94      # BaseOp interface 
 95       
 96 -    def doc(self): 
 97          return __doc__ 
 98   
 99 -    def setup(self): 
100          args = self.args() 
101          position = args.next_int() 
102          if position is not None and args.has_next(): 
103              self.usage() 
104          if position is None: 
105              self._expander = _SequenceExpander(self) 
106          else: 
107              self._expander = _ComponentExpander(self, position) 
108       
109 -    def receive(self, sequence): 
110          self._expander.expand(sequence) 
111   
112 -class _Expander(object): 
113   
114      _command = None 
115   
116 -    def __init__(self, command): 
117          self._command = command 
118   
119 -    def expand(self, sequence): 
120          assert False 
121   
122 -    def contents(self, object): 
123          contents_generator = self._expand_as_file(object) 
124          if not contents_generator: 
125              contents_generator = self._expand_as_sequence(object) 
126          if not contents_generator: 
127              raise _NotExpandableException(object) 
128          return contents_generator 
129   
130 -    def _expand_as_file(self, object): 
131          assert False 
132   
133 -    def _expand_as_sequence(self, object): 
134          if (isinstance(object, tuple) or 
135              isinstance(object, list) or 
136              isinstance(object, types.GeneratorType)): 
137              return self._expand_sequence(object) 
138          else: 
139              return None 
140   
141 -    def _expand_file(self, f): 
142          if isinstance(f, osh.file.File): 
143              filename = f.abspath 
144          else: 
145              filename = f 
146          file = open(filename, 'r') 
147          eof = False 
148          while not eof: 
149              line = file.readline() 
150              if line: 
151                  if line.endswith('\n'): 
152                      line = line[:-1] 
153                  yield line 
154              else: 
155                  eof = True 
156          file.close() 
157   
158 -    def _expand_sequence(self, sequence): 
159          for object in sequence: 
160              yield object 
161   
162 -class _SequenceExpander(_Expander): 
163   
164 -    def __init__(self, command): 
165          _Expander.__init__(self, command) 
166   
167 -    def expand(self, sequence): 
168          for object in self.contents(sequence): 
169              self._command.send(object) 
170   
171 -    def _expand_as_file(self, object): 
172          # Expand as file if object is a sequence of len 1, 
173          # containing a File. 
174          if ((isinstance(object, tuple) or isinstance(object, list)) and len(object) == 1): 
175              object = object[0] 
176          if isinstance(object, osh.file.File): 
177              return self._expand_file(object) 
178          else: 
179              return None 
180   
181 -class _ComponentExpander(_Expander): 
182   
183      _position = None 
184   
185 -    def __init__(self, command, position): 
186          _Expander.__init__(self, command) 
187          self._position = position 
188   
189 -    def expand(self, sequence): 
190          pre = sequence[:self._position] 
191          if self._position == -1: 
192              post = tuple() 
193          else: 
194              post = sequence[(self._position + 1):] 
195          contents = self.contents(sequence[self._position]) 
196          for object in contents: 
197              output = pre + (object,) + post 
198              self._command.send(output) 
199   
200 -    def _expand_as_file(self, sequence): 
201          # Expand as file if item at position is a File. 
202          if isinstance(sequence, osh.file.File): 
203              return self._expand_file(sequence) 
204          else: 
205              return None 
206   
207 -class _NotExpandableException(Exception): 
208   
209      _object = None 
210   
211 -    def __init__(self, object): 
212          self._object = object 
213   
214 -    def __str__(self): 
215          return 'Object of type %s cannot be expanded: %s' % (type(self._object), self._object) 
216