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Python Tips: Using % Locals() – Good Practice?

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Learning Python is a great investment for your future career plans. However, it’s not just about learning the syntax of the language, but also understanding the best practices that come with coding in Python. One of these practices is using the %locals() function in your code.

If you’re unfamiliar with the %locals() function, it’s essentially a way to define local variables within a string format. This can be incredibly helpful when you’re working on complex projects with multiple variables and need to keep track of them all without cluttering your code. However, the question remains: is using %locals() considered good practice?

The answer is yes! In fact, many experienced Python developers swear by the use of %locals() in their code. Not only does it make code more readable, but it also helps prevent coding errors and makes the debugging process much smoother. So don’t be afraid to incorporate %locals() into your Python coding habits.

In conclusion, if you want to become a proficient Python developer, then using %locals() is certainly a tip worth keeping in mind. It’s a simple yet effective way to keep your code clean and maintainable, and it has the potential to save you lots of time in the long run. So if you haven’t already, give %locals() a try and see how it improves your Python coding experience.

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“Python: Is Using “..%(Var)S..” % Locals() A Good Practice?” ~ bbaz


In Python, % locals() is a widely used technique for string formatting. But is it a good practice to use this technique? In this article, we will explore the pros and cons of using % locals() and try to find out whether it is a good practice or not.

What is % Locals()?

% locals() is a special syntax in Python that allows us to insert variables directly into strings. It is known as string interpolation. For example:

“`name = Johnage = 30print(My name is %s and I’m %d years old. % (name, age))“`

Advantages of % Locals()

There are some advantages of using % locals():

Easy to Use

The biggest advantage of % locals() is that it is very easy to use. We can easily insert our variables into strings without having to do any manual formatting.

Readable Code

By using % locals(), our code becomes more readable. It is easier to understand what the code is doing when we see the values of the variables directly in the string.


% locals() is more performant than concatenation or template strings because it doesn’t create any intermediate objects.

Disadvantages of % Locals()

There are some disadvantages of using % locals():

Not Type-Safe

% locals() is not type-safe. It doesn’t do any type-checking, so if we pass the wrong type of variable, we will get a runtime error.

Compatibility Issues

% locals() is not compatible with Python 3.5 and later versions. We should use f-strings instead.

Difficult to Debug

Debugging % locals() can be difficult. It is not always clear which variables are being used in the string, especially if there are a lot of variables or the string is long.

Comparison Table

Advantages Disadvantages
Easy to Use Not Type-Safe
Readable Code Compatibility Issues
Performance Difficult to Debug


After weighing the pros and cons, it seems that % locals() can be a good technique to use, but we should be aware of its limitations. We need to make sure that our code is type-safe and compatible with the latest versions of Python. As long as we use % locals() responsibly, it can be a useful tool in our Python development arsenal.


In my opinion, it is better to use f-strings instead of % locals(). F-strings are more type-safe, more readable, and more performant. They also have the advantage of being compatible with the latest versions of Python. However, if we are working with legacy code that uses % locals(), we should continue to use it carefully.

Thank you for reading our blog about Python Tips and the use of % Locals(). We hope this article provided you with valuable insights on the good practices associated with this approach. As we explored in the article, % Locals() is a highly effective way to simplify code and reduce the risk of bugs occurring.

By taking the time to implement this method properly, you can save yourself a lot of time later on when debugging your code. Additionally, it’s worth noting that this approach is widely used by Python developers around the world, so you can be confident that it’s a tried-and-tested approach.

We encourage you to continue exploring the many other benefits of Python and to experiment with different approaches to see what works best for your individual needs. Should you have any questions or comments about % Locals() or any other aspect of Python development, feel free to reach out to us at any time. Thank you again for reading and we wish you all the best in your Python coding journey!

People also ask about Python Tips: Using % Locals() – Good Practice?

  • What is the purpose of using % locals() in Python?
  • Is using % locals() considered good practice in Python?
  • How does % locals() work in Python?
  • What are the benefits of using % locals() in Python?
  • Are there any drawbacks to using % locals() in Python?


  1. The purpose of using % locals() in Python is to substitute variable values into a string. It allows you to embed variables within a string and dynamically update them based on the values of those variables.
  2. Using % locals() is not necessarily considered good practice in Python. While it can be a useful tool, there are better ways to format strings in Python such as using the .format() method or f-strings.
  3. % locals() works by replacing any variables in a string with their respective values. The syntax for using % locals() is as follows: string with %(variable)s % locals().
  4. The benefits of using % locals() in Python include its flexibility and ease of use for simple string formatting tasks. It can also make code more readable and concise by allowing you to embed variable values directly into a string.
  5. One potential drawback of using % locals() in Python is that it can be less efficient than other string formatting methods for larger strings or when dealing with a large number of variables. Additionally, it can be more prone to errors if variable names are misspelled or if there are conflicts with reserved keywords.