DefaultEnvironment(tools=[])

textlist = ['This line has no substitutions',
            'This line has @subst@ substitutions',
            'This line has %subst% substitutions',
            ]

sub1 = {'@subst@': 'most'}
sub2 = {'%subst%': 'many'}
sub3 = {'@subst@': 'most', '%subst%': 'many'}

env = Environment(tools=['textfile'])

t = env.Textfile('text', textlist)
# no substitutions
s = env.Substfile('sub1', t)
# one substitution
s = env.Substfile('sub2', s, SUBST_DICT=sub1)
# the other substution
s = env.Substfile('sub3', s, SUBST_DICT=sub2)
# the reverse direction
s = env.Substfile('sub4', t, SUBST_DICT=sub2)
s = env.Substfile('sub5', s, SUBST_DICT=sub1)
# both
s = env.Substfile('sub6', t, SUBST_DICT=sub3)