KeyError — how to fix

Traceback (most recent call last):
  File "app.py", line 3, in <module>
    print(user["email"])
          ~~~~^^^^^^^^^
KeyError: 'email'

Quick fix: Use d.get('email') (returns None) or d.get('email', 'default') instead of d['email'], or check first with if 'email' in d:. Print d.keys() to see what keys really exist.

What it means

d["email"] requires the key to exist. It doesn't, so Python raises KeyError with the missing key.

Find out what's actually in the dictionary

print(list(user.keys()))

Common surprises: different case ("Email"), extra whitespace ("email "), the data is nested one level deeper (user["data"]["email"]), or a number vs. string key (1 vs "1").

Fix 1: provide a default

email = user.get("email")              # None if missing
email = user.get("email", "unknown")

Fix 2: check first

if "email" in user:
    send(user["email"])

Fix 3: handle it

try:
    email = user["email"]
except KeyError:
    log.warning("user %s has no email", user.get("id"))

Counting / grouping

Instead of initialising keys manually, use collections.defaultdict or Counter:

from collections import defaultdict
groups = defaultdict(list)
groups[key].append(item)     # no KeyError on first use

pandas: KeyError on a column

df["Price"] raises KeyError: 'Price' if the column name differs. Check df.columns.tolist(); headers often have stray spaces. Clean them with df.columns = df.columns.str.strip().

JSON from an API

APIs often omit fields or return an error object instead of data. Print the response (print(resp.status_code, resp.json())) before indexing into it.

Last updated 2026-10-27.