I want to update my json file using a python script, however the json in the .json file is inside of an array [] it looks like this:
[
{
"test": "2",
"test1": "1"
},
{
"test2": "3",
"test3": "4"
}
]
So far I've tried:
username = "test"
with open("file.json", "a+") as f:
json_file = json.load(f)
json_file[0]['username'] = username
json.dump(json_file, f)
error:
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)```
As @JohnGordon commented, the error occurs on the json_file = json.load(f) line since the file pointer is at the end of file when the file is opened in a+ mode. You can see that when we move the file pointer to the beginning of the file, reading is done successful:
import json
username = "test"
with open("file.json", "a+") as f:
f.seek(0) # move file pointer to the beginning
data = json.load(f)
print(data)
But when you use a+ mode, "the file pointer is returned to the end of file before every write". So when you write to the file, the json data is appended to the end of file, not updating the whole content of the file. So to update your json file, it is more appropriate to use the code below:
import json
username = "test"
with open("file.json", "r") as f:
data = json.load(f)
data[0]['username'] = username
with open("file.json", "w") as f:
json.dump(data, f)
{"username": "test"}, instead of overwriting one that already exists?
data.append({'username': username}) instead of data[0]['username'] = username.AttributeError: 'dict' object has no attribute 'append' when I change it to data[0].append({'username': "test"}) I get KeyError: 0{}, not an empty array []. The error message AttributeError: 'dict' object has no attribute 'append' shows that the read data is a dict not a list.Try separating the 2 actions of opening and closing the file. Like this:
with open("file.json") as obj:
json_file = json.load(obj)
data = json_file[0]
data["username"] = "test"
with open("file.json") as obj:
json.dump(data, obj)
"username": "test"
.jsonyou have provided.usernametestandtest1, both inside a new object inside the arraya+. You're starting at the end of the file, and sojson.load()has nothing to read.