(Fixed) Python TypeError ‘bool’ object is not subscriptable

Problem Formulation

Consider the following minimal example where a TypeError: 'bool' object is not subscriptable occurs:

boo = True
boo[0]
# or:
boo[3:6]

This yields the following output:

Traceback (most recent call last):
  File "C:\Users\xcent\Desktop\code.py", line 2, in <module>
    boo[0]
TypeError: 'bool' object is not subscriptable

Solution Overview

Python raises the TypeError: 'bool' object is not subscriptable if you use indexing or slicing with the square bracket notation on a Boolean variable. However, the Boolean type is not indexable and you cannot slice it—it’s not iterable!

In other words, the Boolean class doesn’t define the __getitem__() method.

boo = True
boo[0]     # Error!
boo[3:6]   # Error!
boo[-1]    # Error!
boo[:]     # Error!

You can fix this error by

1. converting the Boolean to a string using the str() function because strings are subscriptable,
2. removing the indexing or slicing call,
3. defining a dummy __getitem__() method for a custom “Boolean wrapper class”.

🌍 Related Tutorials: Check out our tutorials on indexing and slicing on the Finxter blog to improve your skills!

Method 1: Convert Boolean to a String

If you want to access individual characters of the “Boolean” strings "True" and "False", consider converting the Boolean to a string using the str() built-in function. A string is subscriptable so the error will not occur when trying to index or slice the converted string.

boo = True
boo_string = str(boo)

print(boo_string[0])
# T
print(boo_string[1:-1])
# ru

Method 2: Put Boolean Into List

A simple way to resolve this error is to put the Boolean into a list that is subscriptable—that is you can use indexing or slicing on lists that define the __getitem__() magic method.

bools = [True, True, True, False, False, False, True, False]
print(bools[-1])
# False

print(bools[3:-3])
# [False, False]

Method 3: Define the __getitem__() Magic Method

You can also define your own wrapper type around the Boolean variable that defines a dunder method for __getitem__() so that every indexing or slicing operation returns a specified value as defined in the dunder method.

class MyBool:
    def __init__(self, boo):
        self.boo = boo

    def __getitem__(self, index):
        return self.boo


my_boolean = MyBool(True)

print(my_boolean[0])
# True

print(my_boolean[:-1])
# True

This hack is generally not recommended, I included it just for comprehensibility and to teach you something new. 😉

Summary

The error message “TypeError: 'boolean' object is not subscriptable” happens if you access a boolean boo like a list such as boo[0] or boo[1:4]. To solve this error, avoid using slicing or indexing on a Boolean or use a subscriptable object such as lists or strings.