changing { and } in str.format()

[Gribouillis]

I suggest to use mako templates which need a $ before the {}

>>> from mako.templates import Template
>>> s = "{et{ev}t}d${foo}}tu^tt${bar}tx}"
>>> Template(s).render(foo='hello', bar='world')
'{et{ev}t}dhello}tu^ttworldtx}'
>>> s = "{et{ev}t}d${foo}}tu^tt${bar**3}tx}"
>>> Template(s).render(foo='hello', bar=8)
'{et{ev}t}dhello}tu^tt512tx}'

Of course, there are still issues if the strings contain many % because this is also a part of mako's syntax.