|   | 1 |  initial version  | 
You can use
sage: W = WeylGroup("B2", prefix="s")                                           
sage: w=W.an_element()                                                          
sage: w.to_permutation()                                                        
(2, -1)
And relabel the poset using this map.
|   | 2 |  No.2 Revision  | 
You can use
sage: W = WeylGroup("B2", prefix="s")                                           
sage: w=W.an_element()                                                          
sage: w.to_permutation()                                                        
(2, -1)
And relabel the poset using this map.
EDIT
sage: def new_label(w): 
....:     return ''.join(str(u) for u in w.to_permutation()).replace('-','0')   
sage: W.bruhat_poset().relabel(new_label)                                       
Finite poset containing 8 elements
 Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.
 
                
                Copyright Sage, 2010. Some rights reserved under creative commons license. Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.