python with statement

python 2.5支援with statement,用法像這樣,以open file為例:

printf("xxxx");
with open("x.txt") as f:
  data = f.read()
  do something with data

  因為file object已經有了__enter__()和__exit__()這兩個method,利用with statement就能自動達到像是try-except-finally的程式流程

  若自定class implement __enter__(self)和__exit__(self, type, value, traceback)也能利用with statement來簡化

參考資料:
http://effbot.org/zone/python-with-statement.htm
http://effbot.org/pyref/with.htm