AttributeError Examples

Short, runnable programs that show python attributeerror in action. Read the explanation, press Run, then change the code and try your own ideas. New to the topic? Start with the Python AttributeError lesson.

1Calling a list method on a string

Splitting text gives you a list, but forgetting split() leaves a string. The error names the real type, so you can tell what happened.

Calling a list method on a string

line = "pen,book,lamp"

try:
    line.append("bag")
except AttributeError as err:
    print("AttributeError:", err)

items = line.split(",")
items.append("bag")
print(items)

Expected outputAttributeError: 'str' object has no attribute 'append'
['pen', 'book', 'lamp', 'bag']

2Using the result of an in-place method

append(), sort(), reverse() and update() change the object and return None. Chaining another method after them fails.

Using the result of an in-place method

cart = ["pen"]

try:
    cart.append("book").append("lamp")
except AttributeError as err:
    print("AttributeError:", err)

cart.append("lamp")
print(cart)

prices = [30, 10, 20]
cheapest = sorted(prices)[0]
print(cheapest, prices)

Expected outputAttributeError: 'NoneType' object has no attribute 'append'
['pen', 'book', 'lamp']
10 [30, 10, 20]

3re.match returns None when nothing matches

A pattern search that finds nothing gives None, so calling .group() on it raises AttributeError. Test the match first.

re.match returns None when nothing matches

import re

def order_number(text):
    match = re.search(r"#(\d+)", text)
    if match is None:
        return None
    return int(match.group(1))

print(order_number("Order #482 shipped"))
print(order_number("No number here"))

try:
    re.search(r"#(\d+)", "missing").group(1)
except AttributeError as err:
    print("AttributeError:", err)

Expected output482
None
AttributeError: 'NoneType' object has no attribute 'group'

4A class that forgot to save an attribute

Two constructors for the same data. The broken one never stores balance on self, so reading it fails later, far from the cause.

A class that forgot to save an attribute

class BrokenAccount:
    def __init__(self, owner, balance):
        self.owner = owner
        balance = balance

class Account:
    def __init__(self, owner, balance):
        self.owner = owner
        self.balance = balance

for cls in (BrokenAccount, Account):
    account = cls("Asha", 120)
    try:
        print(cls.__name__, account.owner, account.balance)
    except AttributeError as err:
        print(cls.__name__, "->", err)

Expected outputBrokenAccount -> 'BrokenAccount' object has no attribute 'balance'
Account Asha 120

5getattr() with a default for optional fields

When objects may or may not have an attribute, getattr(obj, name, default) reads it safely. Use it for genuinely optional data.

getattr() with a default for optional fields

class Product:
    def __init__(self, name, discount=None):
        self.name = name
        if discount is not None:
            self.discount = discount

catalog = [Product("pen"), Product("book", discount=15), Product("lamp")]

for product in catalog:
    discount = getattr(product, "discount", 0)
    print(f"{product.name}: {discount}% off")

Expected outputpen: 0% off
book: 15% off
lamp: 0% off

6Listing what an object can do

dir() shows every attribute. Filtering out the names that start with an underscore leaves the methods you would normally call.

Listing what an object can do

text = "python"
numbers = [3, 1, 2]

str_methods = [n for n in dir(text) if n.startswith("s") and not n.startswith("_")]
list_methods = [n for n in dir(numbers) if not n.startswith("_")]

print(str_methods)
print(list_methods)
print("append" in dir(text), "append" in dir(numbers))

Expected output['split', 'splitlines', 'startswith', 'strip', 'swapcase']
['append', 'clear', 'copy', 'count', 'extend', 'index', 'insert', 'pop', 'remove', 'reverse', 'sort']
False True

Practise next

Python AttributeError exercises → Back to the lesson

Python Exceptions: try, except, else and finally examples Python TypeError: What It Means and How to Fix It examples Python NameError examples Python Classes and Objects examples