writing from file into dictionary

[Bo]

Hi all!
I've just started to "play" with Python. Can someone tell me how to
read the grammar in from the file , and place it into a dictionary ?
The grammar is represented by lines where the head is separated from
the rewrite by a colon, as in the following :

start:person does something:
start:I do something:
activity:dancing:
activity:eating:  #and more 

This should be placed into a dictionary...
Thanks a lot, greetings
Bo