Python: replace existing json file

Question

I want to add a new entry in my dictionary but with my code below it overwrites my existing file with the initial dictionary and adds a second dictionary with my new entry. I want to just have one updated dict. My initial dictionary looks like this: Dictionary

This is my code:

@app.route("/add_movie", methods=["POST"])
def add_movie():
    test_title = request.form["title"]
    test_year = request.form["year"]
    new_entry = {"Title": test_title,"Year": test_year,}
    with open("movie_database.json", "r+", encoding="UTF-8") as open_file:
        movie_database = json.load(open_file)
        movie_database.append(new_entry)
        json.dump(movie_database, open_file)
    return render_template("search.html")

Does anybody know what is wrong here?

Lex · Accepted Answer · 2021-05-30 12:10:14Z

1

I believe it's because you used

with open("movie_database.json", "r+", encoding="UTF-8") as open_file:

instead of

with open("movie_database.json", "a", encoding="UTF-8") as open_file:

opening with "a" means append to file

answered May 30, 2021 at 12:10

Lex

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6 Comments

R.Fast Over a year ago

Hi Lex, thanks for your answer. Unfortunately then this error message appears: io.UnsupportedOperation: not readable

Lex Over a year ago

then you must need a+ instead of a

R.Fast Over a year ago

Then a new error appears: json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0). Probably because of my json file.

Lex Over a year ago

Be sure to remember to invoke json.loads() on the contents of the file, as opposed to the file path of that JSON:

Lex Over a year ago

json_file_path = "/path/to/example.json" with open(json_file_path, 'r') as j: contents = json.loads(j.read())

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