python read gzip(.gz) file line by line, compatible with python2 python3

read_gz_file.py

import gzip
gzfile = "example.gz"

# using `with`
with gzip.open(gzfile) as f:
  for i in f:
    i = i.decode('utf-8') # for compatible with python3
    #do sometime
  print(i) 
  
# not `with`
f = gzip.open(gzfile)
lines = f.readlines()
f.close()
lines = [ i.decode('utf-8') for i in lines ] # for compatible with python3
print(lines[-1])