Python

Prevent KeyError when working with dictionaries in Python

Python tip:

You can use .get() to avoid a KeyError when accessing non-existing keys inside a dictionary:

user = {"name": "Jan", "surname": "Giacomelli"}

print(user.get("address", "Best street 42"))
# => Best street 42

print(user["address"])
# => KeyError: 'address'

If you don't provide a default value, .get() will return None if the key doesn't exist.

If you're just trying to see if the key exists, it's better to use the in operator like so due to performance reasons:

# good
if "address" in user:
    print("yay")
else:
    print("nay")

# bad
if user.get("address"):
    print("yay")
else:
    print("nay")