Non-sequential substitution in SymPy

Question

I\'m trying to use [SymPy][1] to substitute multiple terms in an expression at the same time. I tried the [subs function][2] with a dictionary as parameter, but found out that i

Answer 1

Example for @~unutbu's answer:

>>> import ordereddict # collections.OrderedDict in Python 2.7+
>>> from sympy import *
>>> x,y,z = symbols('xyz')
>>> x.subs(ordereddict.OrderedDict([(x,y),(y,z)]))
y
>>> x.subs(ordereddict.OrderedDict([(y,z),(x,y)]))
z