python 分辨文档是不是存有
应用os.path.exists涵数
from os.path import exists
if exists('c.txt'):
with open('c.txt','a') as f:
f.write('www.h3blog.com')
f.close()
else:
with open('c.txt','a') as f:
f.write('www.h3blog.com')
f.close()
