Json File Handling in Python: Writing input to file

Question

this is my code that Im trying to get to write into a JSON file in the format {"Example1": "Example"} Im getting an error which reads:

db_file.write(json.dump({"Admin": keyPass}, db_file)) TypeError: must be str, not None

For this code:

         keyPass = input("Create Admin Password » ")                    
         with codecs.open(os.path.join(PATH), 'w') as db_file:
             db_file.write(json.dump({"Admin": keyPass}, db_file))

This is the weird part, it creates it in the file fine and how I want it to be formatted is correct, yet it still comes up with the error above.

Could anyone please help me with what I need to correct here?

Warren Spencer · Accepted Answer · 2015-10-10 18:41:19Z

4

The first two arguments to the json.dump function are:

obj: The object to serialize
fp: A file-like object to write the data to

So what's happening here, is the inner call to json.dump is successfully writing the JSON-encoded string to your file, but then you're trying to pass the output of it (which will always be None) to your fileobject's write function.

You have two options:

use json.dumps(stringToEncodeAsJSON) instead of json.dump, which will return the JSON formatted string which can then be written to your file using your fileObject's write function
Remove the fileObject's write function from around the json.dump call

Update:

Here are some examples of how you could do it

keyPass = input("Create Admin Password > ")

with open(pathName, 'w') as db_file:
    db_file.write(json.dumps({"Admin": keyPass}))

with open(pathName, 'w') as db_file:
    json.dump({"Admin": keyPass}, db_file)

edited Oct 10, 2015 at 18:41

answered Oct 10, 2015 at 17:05

Warren Spencer

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5 Comments

Csarg Over a year ago

Whats wrong with this: with codecs.open(os.path.join(PATH), 'w') as db_file: json.dump({"Admin": keyPass})

Warren Spencer Over a year ago

Is that related to the original question? You're calling json.dump but not passing in the file pointer argument, which is required

Csarg Over a year ago

I was trying to fix the problem, but I don't think I understand it.

Warren Spencer Over a year ago

Let me give you a few examples

Csarg Over a year ago

Ahh, I understand the problem now.. Thank you. I guess I'm tired.. xD

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