Understanding Why the False == True and not True Expression Returns False in Python

Discover the underlying logic of boolean expressions in Python, particularly why `False == True and not True` evaluates to `False`.
---
This video is based on the question https://stackoverflow.com/q/69064111/ asked by the user 'Emily' ( https://stackoverflow.com/u/16835708/ ) and on the answer https://stackoverflow.com/a/69064134/ provided by the user 'I'mahdi' ( https://stackoverflow.com/u/1740577/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Why does this boolean expression return False?

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Unpacking Python Boolean Logic: The Case of False == True and not True

When working with boolean expressions in Python, it’s crucial to fully grasp how these expressions are evaluated. A common point of confusion is illustrated by the expression False == True and not True. Let's dive into why this expression returns False, even if we initially expect it to return True.

The Expression Breakdown

The Complete Expression

The expression in question is:

[[See Video to Reveal this Text or Code Snippet]]

At first glance, one might assume that this expression could yield True due to the presence of both False and True. However, let’s break down the components to understand why this is not the case.

Understanding Boolean Operators

In Python, boolean expressions are evaluated using three main operators:

==: Checks for equality

and: Logical AND operator

not: Logical NOT operator

These operators follow specific rules of precedence, which dictate the order in which the operations are performed. It's important to evaluate the expressions step-by-step.

Step-by-Step Evaluation

Let’s evaluate the expression False == True and not True step-by-step:

Evaluate not True:

The logical NOT operator negates the value of a boolean expression. Since True is provided, not True evaluates to False.

[[See Video to Reveal this Text or Code Snippet]]

Substituting the Values:

Now, substitute not True back into the original expression:

[[See Video to Reveal this Text or Code Snippet]]

Evaluate False == True:

This portion of the expression checks whether False is equal to True. Clearly, this is False.

[[See Video to Reveal this Text or Code Snippet]]

Combining with the and Operator:

Now, combine the results using the and operator:

[[See Video to Reveal this Text or Code Snippet]]

The result of False and False is False, because both conditions need to be True for an and operation to return True.

Conclusion

The final output of the expression print(False == True and not True) is indeed False.

To summarize:

The comparison of False == True evaluates to False.

The negation not True gives us False.

Therefore, False and False results in False.

Key Takeaway

It’s essential to understand the order of operations in boolean logic and how different operators interact. By breaking down expressions into manageable parts, one can avoid confusion and correctly anticipate the output.

Understanding boolean expressions is a critical skill for anyone working with Python, and the case of False == True and not True serves as an enlightening example.