ファイルを一行ずつ読み取るPythonの実装方法【小さいファイルと大きいファイルの読み取り】

#coding=utf-8
#author: walker
#date: 2013-12-30
#function: 按行读取小文件
all_lines = []
try:
  file = open('txt.txt', 'r')
  all_lines = file.readlines()
except IOError as err:
  print('File error: ' + str(err))
finally:
  if 'file' in locals():
    file.close()
for line in all_lines:
  print(line)

#coding=utf-8
#author: walker
#date: 2013-12-30
#function: 按行读取大文件
try:
  file = open('txt.txt', 'r')
  for line in file:
    print(line)
except IOError as err:
  print('File error: ' + str(err))
finally:
  if 'file' in locals():
    file.close()