Converting unix timestamp string to readable date

I have a string representing a unix timestamp (i.e. "1284101485") in Python, and I'd like to convert it to a readable date. When I use time.strftime, I get a TypeError:

>>>import time
>>>print time.strftime("%B %d %Y", "1284101485")

Traceback (most recent call last):
  File "", line 1, in 
TypeError: argument must be 9-item sequence, not str