TypeError: list indices must be integers or slices, not str — decoded

What this message means

A list is an ordered sequence: its only addressing scheme is a position — items[0], items[-1], items[1:4]. A string inside the brackets is a *key*, and keys belong to dictionaries, not lists. When Python sees prices["apple"] and prices is a list, it raises this TypeError with the exact rule you broke.

The two usual stories behind it: the data really is a list and you should use a position or a loop — or the data should have been a dict and somewhere along the way you (or a JSON response) built the wrong shape.

Traceback (most recent call last):
  File "main.py", line 4, in <module>
    print(prices["apple"])
          ~~~~~~^^^^^^^^^^
TypeError: list indices must be integers or slices, not str

A real example

prices = [40, 55, 30]          # a list — positions only
print(prices["apple"])         # a key — dicts only

The fix depends on which shape you *meant*. If the names matter, build a dict. If the order is enough, use the index:

prices = {"apple": 40, "banana": 55, "cherry": 30}
print(prices["apple"])         # 40

# or keep the list and use positions
print(prices_list[0])          # 40

The JSON edition of this bug

JSON objects become dicts and JSON arrays become lists — so the same URL can hand you either shape on a different day. data["items"][0]["name"] is correct when items is an array of objects, but fails with this error the moment items is a list and you skip the [0]:

data = {"items": [{"name": "pen"}, {"name": "ink"}]}

print(data["items"]["name"])    # TypeError — items is a LIST
print(data["items"][0]["name"]) # pen — subscript the list first

When a request returns something unexpected, print the type at each level — type(data), type(data["items"]) — until the shape in your head matches the shape in memory.

The causes behind almost every case

• List of dicts mistaken for a dict of dicts. rows["id"] fails; rows[0]["id"] is what a list of records needs.
• Iterating keys over a list. for key in keys: total += prices[key] is fine only when prices is a dict — inside a loop it is easy to lose track.
• A variable name that lies. menu["tea"] reads naturally, so the mistake hides — until you check and menu is a list of names, not a mapping.
• Converting between shapes. Turning a dict into list(d) gives you its *keys* as a list; indexing that with a string then fails.

The fix, step by step

1. Print type(container) — confirm it is really a list and not the dict you assumed.
2. If it is a list of records, subscript twice: first a position, then the key — rows[0]["name"].
3. If you need name-based access, build the dict you wanted: prices = {item["name"]: item["price"] for item in items}.
4. If the loop was the problem, iterate the list directly — for item in items: — instead of generating indices or keys.

Related messages worth knowing

• TypeError: the parent guide — the parent explainer for every wording of this exception.
• KeyError — the mirror mistake on the dict side — a key that does not exist.
• IndexError: list index out of range — the sibling message when the index is valid type but the position does not exist.

Fix it interactively

These free problems practice choosing between positions and keys — the exact decision this error is about:

• Accessing a missing dictionary key easy
• Nested dictionary access medium