Python > Modules and Packages > Modules > Importing Modules (`import` statement)

Selective Module Import

This snippet demonstrates how to import specific functions or constants from a module using the from ... import statement. This is useful when you only need a few items from a module and want to avoid the verbosity of the basic import.

Code Example

This code imports only the sqrt function and the pi constant from the math module. You can now use them directly in your code without prefixing them with math..

from math import sqrt, pi

# Now you can use sqrt and pi directly without the math. prefix
result = sqrt(25)
print(result)  # Output: 5.0

circle_area = pi * 10**2
print(circle_area)

Concepts Behind the Snippet

The from ... import statement directly imports the specified names into your current namespace. This can make your code more concise but also introduces the risk of naming conflicts if the imported names clash with existing names in your code.

Real-Life Use Case Section

If you're working on a project where you only need a specific function from a large library, selective import can improve code readability by reducing verbosity. For example, if you only need the json.loads function from the json module, you can import it directly.

Best Practices

  • Avoid Importing Everything: Avoid using from module import *. This imports all names from the module into your current namespace, which can lead to naming conflicts and make your code harder to understand.
  • Be Mindful of Naming Conflicts: If you're importing multiple names from different modules, be aware of potential naming conflicts and consider aliasing names using as if necessary.

When to use them

Use selective imports when you only need a small subset of a module's functionality and you want to avoid the verbosity of the basic import statement. Be mindful of potential naming conflicts.

Memory Footprint

In theory, selectively importing only parts of a module should reduce the memory footprint compared to importing the entire module. However, in practice, the difference might be negligible for most standard modules, as Python often loads the entire module anyway. The key benefit is more about code clarity and avoiding namespace pollution.

Alternatives

An alternative is basic import (import math). Another alternative is to import the whole module and use alias import math as m then use m.sqrt()

Pros

  • Conciseness: Code is more compact and easier to read.
  • Potential Memory Savings: May slightly reduce memory usage compared to importing the entire module (though the effect is often negligible).

    • Cons

  • Naming Conflicts: Can lead to naming collisions if imported names clash with existing names in your code.
  • Reduced Clarity (Sometimes): It can be less clear where a function or constant comes from if you don't explicitly see the module name.

    • ← Reloading a Module with `importlib.reload()` Simple HTTP Request with `urllib` →

    FAQ

    • What happens if I try to import a name that doesn't exist in the module?

      You'll get an ImportError.
    • Can I alias an imported name?

      Yes, you can use the as keyword to give an imported name a different alias: from math import sqrt as square_root. Now you can use square_root() instead of sqrt().