pretty printing graphs

[Michele Simionato]

Here is an enhanced version that also draws the metaclass instantiation
relationship:

import os

def label(i,n):
    if n>1: return '[label="%s"]' % (i+1)
    return ""

def dotMRO(cls):
    "Generate the dot code for the MRO directed graph"
    yield "digraph MRO_of_%s{\n" % cls.__name__
    for c in cls.__mro__:
        n=len(c.__bases__)
        yield ' '.join([
            '    edge [style=solid]; %s -> %s %s;' %
            (b.__name__,c.__name__,label(i,n))
            for i,b in enumerate(c.__bases__)])
        if type(c) is not type:  yield \
           '  edge [style=dashed]; %s -> %s;' % (type(c).__name__,c.__name__)
    yield '}'

class M(type): pass
O=object
class F(O): pass
class E(O): pass
class D(O): pass
class G(O): __metaclass__=M
class C(F,D,G): pass
class B(E,D): pass
class A(B,C): pass

dotcode='\n'.join(dotMRO(A)); print dotcode
os.system('echo "%s" | dot -Tps > prova.ps' % dotcode)
os.system('gv prova.ps&')

See the graph at

http://www.phyast.pitt.edu/~micheles/prova.ps

Here I had a problem due to my lack of knowledge of "dot":
class C inherits from F,D and G (in this order, see the labels
1,2,3). However, "dot" draws D before F and, without looking
at the labels, one would think that D comes before F, which
is not the case. IOW, the line FC should cross the line DC,
and the F-arrow should be on the left of the D-arrow.
Is there any way of fixing that? 

TIA,


                        Michele