def readInChunks(fileObj, chunkSize=4096):
"""
Lazy function to read a file piece by piece.
Default chunk size: 4kB.
"""
while 1:
data = fileObj.read(chunkSize)
if not data:
break
yield data
f = open('bigFile')
for chuck in readInChunks(f):
#do_something(chunk)
f.close()