Pass Exception to next except statement

Question

I'm catching exceptions with a try...except block in Python. The program tries to create a directory tree using os.makedirs. If it raises WindowsError: directory already exists, I want to catch the exception and just do nothing. If any other exception is thrown, I catch it and set a custom error variable and then continue with the script. What would theoretically work is the following:

try:
    os.makedirs(path)
except WindowsError: print "Folder already exists, moving on."
except Exception as e:
    print e
    error = 1

Now I want to enhance this a bit and make sure that the except block for WindowsError only treats those exceptions where the error message contains "directory already exists" and nothing else. If there is some other WindowsError I want to treat it in the next except statement. But unfortunately, the following code does not work and the Exception does not get caught:

try:
    os.makedirs(path)
except WindowsError as e: 
    if "directory already exists" in e:
        print "Folder already exists, moving on."
    else: raise
except Exception as e:
    print e
    error = 1

How can I achieve that my first except statement specifically catches the "directory already exists" exception and all others get treated in the second except statement?

Answer 1

Use one exception block and special case your handling there; you can just use isinstance() to detect a specific exception type:

try:
    os.makedirs(path)
except Exception as e:
    if isinstance(e, WindowsError) and "directory already exists" in e:
        print "Folder already exists, moving on."
    else:
        print e
        error = 1

Note that I'd not rely on the container-like nature of exceptions here; I'd test the args attribute explicitly:

if isinstance(e, WindowsError) and e.args[0] == "directory already exists":