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

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

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Problem Formulation

Consider the following minimal example where a

Code:

TypeError: 'bool' object is not subscriptable

occurs:

Code:

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

This yields the following output:

Code:

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

Code:

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

Code:

__getitem__()

method.

Code:

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
   Code:

   str()
   function because strings are subscriptable,
   
   
2. removing the indexing or slicing call,
   
   
3. defining a dummy
   Code:

   __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

Code:

"True"

and

Code:

"False"

, consider converting the Boolean to a string using the

Code:

str()

built-in function. A string is subscriptable so the error will not occur when trying to index or slice the converted string.

Code:

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

Code:

__getitem__()

magic method.

Code:

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

Code:

__getitem__()

so that every indexing or slicing operation returns a specified value as defined in the dunder method.

Code:

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 “

Code:

TypeError: 'boolean' object is not subscriptable

” happens if you access a boolean

Code:

boo

like a list such as

Code:

boo[0]

or

Code:

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.