1.python 语法对 空格，缩进有严格要求
2.file objects contain a special pair of built-in methods: __enter__() and__exit__()
__enter__()
__exit__()
such as:
with open("text.txt", "w") as v: v.write("sss")
python_code_420
原文：http://www.cnblogs.com/njuzwr/p/4440726.html
