python:with的简单用法详解

with在python中可以用来结束文件（f.close()）
例如

try:
  f = open('data.txt','w')
  for each_line in f:
            print(each_line)
except OSError as reason:
    print("出错了"+str(reason))
finally:
   f.close()

try:
    with open('data.txt','w') as f:
        for each_line in f:
            print(each_line)
except OSError as reason:
    print("出错了"+str(reason))