Let's say you want to know what the Python program is for the Sage command to compute the center of a permutation group. Use Sage's help interface to find the file name:
sage: ?PermutationGroup.center Type: instancemethod Base Class: <type 'instancemethod'> String Form: <unbound method PermutationGroup.center> Namespace: Interactive File: /home/wdj/sage/local/lib/python2.4/site-packages/sage/groups/permgroup.py Definition: PermutationGroup.center(self)
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