Source Code for Module roslib.params

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33  # Revision $Id: params.py 7386 2009-12-17 01:49:35Z kwc $ 
34  # $Author: kwc $ 
35  """ 
36  Utilities for accessing the Parameter Server 
37  """ 
38   
39  import sys 
40  import xmlrpclib 
41   
42  import roslib.rosenv 
43  from roslib.names import REMAP 
44   
45  _param_server = None 
46   
47 -def load_command_line_node_params(argv): 
48      """ 
49      Load node param mappings (aka private parameters) encoded in 
50      command-line arguments, e.g. _foo:=bar. See also roslib.names.load_mappings. 
51      @param argv: command-line arguments 
52      @param argv: [str] 
53      @return: param->value remappings.  
54      @rtype: {str: val} 
55      """     
56      try: 
57          import yaml 
58      except ImportError, e: 
59          print >> sys.stderr, "Cannot import yaml. Please make sure the pyyaml system dependency is installed" 
60          raise e 
61      mappings = {} 
62      for arg in argv: 
63          if REMAP in arg: 
64              try: 
65                  src, dst = [x.strip() for x in arg.split(REMAP)] 
66                  if src and dst: 
67                      if len(src) > 1 and src[0] == '_' and src[1] != '_': 
68                          mappings[src[1:]] = yaml.load(dst) 
69              except: 
70                  print >> sys.stderr, "ERROR: Invalid remapping argument '%s'"%arg 
71      return mappings 
72   
73 -def get_param(key): 
74      """ 
75      Retrieve parameter value from the Parameter Server. Each call to this 
76      routine results in an actual network call to the Parameter Server. 
77      Client must be an actual ROS node in order to implement a parameter cache. 
78   
79      @param key: name of parameter to fetch 
80      @type  key: str 
81      @raise KeyError: if parameter is not set 
82      """ 
83      global _param_server 
84      if _param_server is None: 
85          _param_server = xmlrpclib.ServerProxy(roslib.rosenv.get_master_uri()) 
86      code, status, value = _param_server.getParam('/roslib', key) 
87      if code != 1: #unwrap value with Python semantics 
88          raise KeyError(key) 
89      return value 
90