python json序列化try / except

Question

I'm trying to serialize a trivial object (only attributs / values), I have this methode in my class.

def to_json(self,client):
    service=self._service
    path="jsonphp/"
    path+=client
    if not os.path.exists(path):
        os.makedirs(path)
    with cdd(path):
      print os.getcwd()
      path=service+".json"
      with open(path, 'w') as outfile:
        try:
          json.dump(self.__dict__, outfile)
        except:
          print "serialization failed"

the whole part before the try/except is to naviguate to the correct folder. It seems to work smoothly. But when I use this methode, it always print : serialization failed from my except even tho my file.json is created and the data are correctly stored in it : {"_attr1": "On", "_attr2": "On", "_attr3": "Off"} I thought the except block was only visited if an error had occured.

My questions are the fallowing : is that the "normal" behaviour of try/except ?

If not, how to have information about the exception that my except is catching ?

Could it be an exeption from somewhere upper in the code (before I call to_json() ) that is catched there ?

Answer 1

I find this to be more of an exception handling question than anything else. Since you're likely to have exceptions throughout your programming endeavors, it's important to handle them properly. Rarely should the except be so broad, and in the case where you don't understand why there is an exception, you should be printing the exception. This will give you the ability to search for the exception and determine what the root cause of your problem is and will help you greatly as you continue to learn Python.

Change your except to read:

except Exception as e:
          print "serialization failed", e

This will print the exact exception to your console and allow you to look up, or ask for help.