# 1f = open('fileName', 'r')# do something with ff.close()# 2with open('fileName', 'r') as f:# do something with f# no need to close, and will close automatically if exception rised

lines = f.readlines()for line in lines:fun(line)

for line in f:fun(f)

line = f.readline()while line:fun(line, f) # can read more line by f.readline()line = f.readline()