variable length print format

[les ander]

Hi,
i have a variable length list of numbers.
i would like to print them out with indicies in front as shown below:

List=['a','b','c','d'] ---> 1:a 2:b 3:c 4:d

one obvious solution is that i do
for i in range(List):
  print "%s:%s" % (i+1,List[i])

however i have a lot of these and would like it to be faster so i 
tried doing this 

formatstr=" %s:%s " * len(List)

print formatstr % (range(1,len(List)+1), List)

but it did not work.

is there a way to do this another way?
les