If time format isn't really important to you, this will do:
>>> from time import ctime as convert
>>> convert(1284101485)
'Fri Sep 10 10:51:25 2010'
Example of usage:
number = 1000
# Here we generate a list with given number of timestamps.
from random import randint
timestamps = []
for i in range(0, number):
timestamps += [randint(0, 2147483647)]
# Here is actual example of massive conversation.
from time import ctime as convert
for i in range(0, number):
print(str(i+1)+"\t"+str(timestamps[i])+"\t->\t"+convert(timestamps[i]))
Example generates a list with timestamps (ready-to-use data). Next we convert timestamps (in loop) and print them. Code processes (generates, converts and prints) 200 timestamps faster than I can blink, 1k timestamps in less than 0.5 second and 100k in less than 12 seconds. Tested on old PC.