TypeError: string indices must be integers

Diagnose this error in under a minute

Before changing anything, print the value's type — it points straight to the fix you need:

print(type(data))
print(repr(data)[:200])

• <class 'str'> → it's JSON text — parse it first with json.loads() / response.json() (Cause 1)
• <class 'dict'> → you're looping over it (keys are strings) or using a wrong key — iterate .values() / .items() (Cause 2)
• <class 'list'> → index by number first, then by key: data[0]['key'] (Cause 3)
• still a str after one json.loads → the payload was double-encoded — parse again or fix the producer (Cause 4)

The exact error string

data = '{"name": "Ada", "age": 36}'   # this is a STRING, not a dict
print(data['name'])

Traceback (most recent call last):
  File "app.py", line 2, in <module>
    print(data['name'])
TypeError: string indices must be integers, not 'str'

Python read data['name'] as "give me index 'name' of this string," and string indexes must be integers like data[0]. The not 'str' suffix (Python 3.11+) confirms you handed it a string index.

Where you'll usually see this

It almost always appears at the boundary where text becomes data — the same root cause across the Python web stack:

• requests — using resp.text instead of resp.json()
• Flask / FastAPI / Django — reading a raw request body without parsing it
• AWS Lambda — event['body'] arrives as a JSON string; parse it before indexing
• config & JSON files — f.read() returns text; use json.load(f) instead

Cause 1: you forgot to parse the JSON

A response body, a file's contents, or a message payload is text. Until you parse it, indexing by key fails:

import json, requests

resp = requests.get("https://api.example.com/user")

# ❌ resp.text is a JSON string
data = resp.text
data["name"]                      # TypeError: string indices must be integers

# ✅ parse it into a dict first
data = resp.json()                # or json.loads(resp.text)
data["name"]                      # 'Ada'

The same applies to files: use json.load(f) (parses) rather than f.read() (returns text). If you are not sure what the payload looks like, paste it into the JSON Formatter to see whether it is an object you can key into.

Cause 2: looping over a dict gives you keys

Iterating a dict yields its keys — which are strings — so indexing the loop variable fails:

users = {"u1": {"name": "Ada"}, "u2": {"name": "Bo"}}

# ❌ item is the key string "u1", so item["name"] fails
for item in users:
    print(item["name"])           # TypeError: string indices must be integers

# ✅ iterate values (or items) to get the inner dicts
for user in users.values():
    print(user["name"])           # 'Ada', 'Bo'

for key, user in users.items():
    print(key, user["name"])

Cause 3: a list of dicts indexed wrong

If the data is a list of objects, you must index the list by number first, then the object by key — not the other way round:

rows = [{"name": "Ada"}, {"name": "Bo"}]

rows["name"]                      # ❌ rows is a list — wrong
rows[0]["name"]                   # ✅ 'Ada'
for row in rows:                  # ✅ each row is a dict
    print(row["name"])

Cause 4: double-encoded JSON

If one json.loads still leaves you with a string, the payload was encoded twice — a value that is itself a JSON string:

raw = '"{\\"name\\": \\"Ada\\"}"'   # a JSON string whose content is JSON

once = json.loads(raw)             # -> '{"name": "Ada"}'  (still a str!)
once["name"]                       # TypeError again

twice = json.loads(once)           # -> {'name': 'Ada'}
twice["name"]                      # 'Ada'  — but fix the producer if you can

Errors often confused with this one

These Python errors come from the same family of "wrong type / wrong shape" mix-ups:

• TypeError: the JSON object must be str, bytes or bytearray, not dict — the inverse: parsing something that's already parsed
• KeyError — the value is a dict, but the key is missing
• JSONDecodeError — the text isn't valid JSON to begin with
• AttributeError: 'str' object has no attribute ... and IndexError — the same "I assumed the wrong type" confusion, on a string or a list

Debugging checklist

• ✓ Print type(data) — is it str or dict?
• ✓ str that looks like JSON? Run json.loads() / response.json() first
• ✓ In a for loop over a dict? Iterate .values() or .items()
• ✓ Is it a list of dicts? Index by number first: data[0]['key']
• ✓ Still a string after one parse? It was double-encoded — parse again or fix the source
• ✓ Inspect the real shape in the JSON Formatter