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Python JSON

Brett McGregor
PLUS
Brett McGregor
Courses Plus Student 1,903 Points
Posted by Brett McGregor
Brett McGregor
Courses Plus Student 1,903 Points

read JSON file error: " list indices must be integers or slices, not str"

So, here is my code to read a JSON file. 

import json

with open("example.json") as file:
    db = json.load(file)
    print(db["supplier"])

and here is the JSON file I found to work with:

[{
  "_id": {
    "$oid": "5968dd23fc13ae04d9000001"
  },
  "product_name": "sildenafil citrate",
  "supplier": "Wisozk Inc",
  "quantity": 261,
  "unit_cost": "$10.47"
}, {
  "_id": {
    "$oid": "5968dd23fc13ae04d9000002"
  },
  "product_name": "Mountain Juniperus ashei",
  "supplier": "Keebler-Hilpert",
  "quantity": 292,
  "unit_cost": "$8.74"
}, {
  "_id": {
    "$oid": "5968dd23fc13ae04d9000003"
  },
  "product_name": "Dextromathorphan HBr",
  "supplier": "Schmitt-Weissnat",
  "quantity": 211,
  "unit_cost": "$20.53"
}]

Python gives me the following error:

Traceback (most recent call last):
  File "C:/Python36-32/Scripts/read_JSON.py", line 5, in <module>
    print(db["supplier"])
TypeError: list indices must be integers or slices, not str

My code is exactly the same as Kenneth used in the video. I guess the JSON file I am using is somehow different to the one Kenneth used in his example.

Brett McGregor
Brett McGregor
Courses Plus Student 1,903 Points
Brett McGregor
Brett McGregor
Courses Plus Student 1,903 Points

I have just noticed that my JSON file is enclosed in square brackets. I suppose that makes it a list, which explains my error.

I tried with a different JSON file and was able to return data.

I guess I need to learn more about this topic!!!

1 Answer

Oszkár Fehér
seal-mask
.a{fill-rule:evenodd;}techdegree seal-36
Oszkár Fehér
Treehouse Project Reviewer
Oszkár Fehér
.a{fill-rule:evenodd;}techdegree seal-36
Oszkár Fehér
Treehouse Project Reviewer

Hi Brett. It gives you that error because when you print the "db" variable with the keyword "supplier" it looks in a dictionary 

print(db["supplier"])

but "db" actually is a list, and on list you can use or integer or slices, like

db[0]

where the number indicates the position of the item but if you cal

db[0]["supplier"]

then it will look for the first item keyword "supplier" and gives you back one item. I checked for slices and i'm not sure why it gives error for slice for ex:

db[:]["supplier"]

So the solution if you want all the suppliers from the json file you have to make a for loop on "db"

items = []
for item in db:
    items.append(item['supplier'])
print(items)

or

print([db_item["supplier"] for db_item in db])

And you get the desired result. I hope it helps you to understand. Happy coding