interpolate local and global variables into string.
arguments:
- s (string)
template string with $var or ${var} placeholders
- iframe (int) (optional, default=1)
frame index (1=calling frame, 2=callers calling frame, etc.)
example:
>>> import decida
>>> x = 23
>>> a = "ten"
>>> t = decida.interpolate("""
... a : $a
... x : $x
... """)
>>> print t
a : ten
x : 23