How To Disable Assertions In Python Production Code for Improved Performance

Python’s `assert` statement is a valuable tool for debugging and ensuring code correctness during development. However, in production environments, the overhead of checking assertions can impact performance. To optimize your production code, it’s essential to disable assertions. In this article, we’ll explore how to disable assertions in Python production code using practical examples and discuss the benefits of doing so.

Table of Contents

1. The Role of Assertions in Development.

Assertions are invaluable during the development phase of software engineering. They help detect and handle unexpected issues, ensuring that code behaves as expected.

However, when your code reaches the production stage, excessive assertion checks can negatively affect performance and efficiency.

2. Disabling Assertions Using the `-O` Command-Line Switch.

One way to disable assertions in Python production code is by using the `-O` (optimize) command-line switch.
This switch instructs Python to exclude `assert` statements and their associated expressions when running in optimized mode.

To use this approach, follow these steps:
Open your terminal or command prompt.
Navigate to the directory containing your Python script.

Run your Python script with the `-O` switch, like this:
```
python -O your_script.py
```
Replace `your_script.py` with the name of your Python script.

2.1 Example:

Let’s consider a simple script that includes an assertion:

# disable_assertion.py

def divide(a, b):
    assert b != 0, "Division by zero is not allowed"
    return a / b

result = divide(10, 0)
print(result)

To run this script without assertion optimization, use the following command python .\disable_assertion.py, you can see the exception is thrown by the assert statement.

PS D:\WorkSpace\Work\python-courses\python-flow-control> python .\disable_assertion.py
Traceback (most recent call last):
  File "D:\WorkSpace\Work\python-courses\python-flow-control\disable_assertion.py", line 7, in <module>
    result = divide(10, 0)
  File "D:\WorkSpace\Work\python-courses\python-flow-control\disable_assertion.py", line 4, in divide
    assert b != 0, "Division by zero is not allowed"
AssertionError: Division by zero is not allowed

To run this script with assertion optimization, use the following command python -O .\disable_assertion.py, you can see the exception is not thrown by the assert statement.

PS D:\WorkSpace\Work\python-courses\python-flow-control> python -O .\disable_assertion.py
Traceback (most recent call last):
  File "D:\WorkSpace\Work\python-courses\python-flow-control\disable_assertion.py", line 7, in 
    result = divide(10, 0)
  File "D:\WorkSpace\Work\python-courses\python-flow-control\disable_assertion.py", line 5, in divide
    return a / b
ZeroDivisionError: division by zero

3. Disabling Assertions Using the `PYTHONOPTIMIZE` Environment Variable.

Alternatively, you can set the `PYTHONOPTIMIZE` environment variable to enable assertion optimization globally for all Python scripts run in the current environment. Here’s how to do it:

On Unix/Linux/macOS:
```
export PYTHONOPTIMIZE=1
```
On Windows (Command Prompt):
```
set PYTHONOPTIMIZE=1
```
On Windows (PowerShell):
```
$env:PYTHONOPTIMIZE=1
```
After setting the environment variable, you can run your Python scripts as usual, and Python will automatically optimize them by excluding `assert` statements.

Below is an example of using the global environment variable PYTHONOPTIMIZE.

D:\WorkSpace\Work\python-courses\python-flow-control>set PYTHONOPTIMIZE=1

D:\WorkSpace\Work\python-courses\python-flow-control>python .\disable_assertion.py
Traceback (most recent call last):
  File "D:\WorkSpace\Work\python-courses\python-flow-control\disable_assertion.py", line 7, in <module>
    result = divide(10, 0)
  File "D:\WorkSpace\Work\python-courses\python-flow-control\disable_assertion.py", line 5, in divide
    return a / b
ZeroDivisionError: division by zero

D:\WorkSpace\Work\python-courses\python-flow-control>set PYTHONOPTIMIZE=0

D:\WorkSpace\Work\python-courses\python-flow-control>
D:\WorkSpace\Work\python-courses\python-flow-control>python .\disable_assertion.py
Traceback (most recent call last):
  File "D:\WorkSpace\Work\python-courses\python-flow-control\disable_assertion.py", line 7, in <module>
    result = divide(10, 0)
  File "D:\WorkSpace\Work\python-courses\python-flow-control\disable_assertion.py", line 4, in divide
    assert b != 0, "Division by zero is not allowed"
AssertionError: Division by zero is not allowed

4. Benefits of Disabling Assertions in Production.

Improved Performance: By removing assertion checks, your code can run faster and more efficiently in production environments.

Reduced Memory Usage: Excluding assertion-related code reduces memory consumption, making your application more resource-friendly.
Reduced Attack Surface: Disabling assertions can also improve security by minimizing the opportunities for potential attackers to exploit assertion failures.

5. A Word of Caution.

While disabling assertions in production can provide performance benefits, it’s crucial to do so only when you are confident that your code is error-free and your software is stable.

During development and debugging phases, it’s recommended to keep assertions enabled to catch issues early and ensure the correctness of your code.

6. Conclusion.

Optimizing Python production code by disabling assertions is a straightforward yet powerful way to enhance performance and resource efficiency.
Whether you choose to use the `-O` command-line switch or set the `PYTHONOPTIMIZE` environment variable, taking this step can help your code run smoother and more reliably in production environments, delivering a better experience to your users while maintaining confidence in the stability of your software.