Race-condition creating folder in Python

Question

I have a urllib2 caching module, which sporadically crashes because of the following code:

if not os.path.exists(self.cache_location):
    os.mkdir(self.cach         


        

Answer 1

In Python 3.x, you can use os.makedirs(path, exist_ok=True), which will not raise any exception if such directory exists. It will raise FileExistsError: [Errno 17] if a file exists with the same name as the requested directory (path).

Verify it with:

import os

parent = os.path.dirname(__file__)

target = os.path.join(parent, 'target')

os.makedirs(target, exist_ok=True)
os.makedirs(target, exist_ok=True)

os.rmdir(target)

with open(target, 'w'):
    pass

os.makedirs(target, exist_ok=True)