5 Best Ways to Import Functions in Python

💡 Problem Formulation: When working with Python, there are times when you need to use a function that is not in the current scope of your script or notebook. In this article, we’ll explore how to import these functions from various sources like modules, packages, and even other scripts. Imagine needing a mathematical function from the math module, or a date handler from the datetime library; we’ll show you exactly how to bring these into your workspace.

Method 1: Importing a Single Function from a Module

This method involves importing just a single function from a module, which can be efficient if that’s all you need. Using this method reduces memory usage as only the specific function is loaded into the namespace.

Here’s an example:

from math import sqrt
print(sqrt(16))

Output:
4.0

In the example above, we import the sqrt function from the math module, which calculates the square root of a number. Since only sqrt is imported, calling the function doesn’t require the math. prefix.

Method 2: Importing All Functions from a Module

This method imports all the functions and variables defined in a module. It’s useful if you need multiple things from the module, yet it can lead to a cluttered namespace and potential naming conflicts.

Here’s an example:

from datetime import *
print(date.today())
print(time(12, 34))

Output:
YYYY-MM-DD
12:34:00.000000

We import all the classes and functions from the datetime module, allowing us to use date.today() and time() directly without prefixing them with datetime..

Method 3: Importing a Module with an Alias

Using an alias for a module can save typing time and improve code readability, especially if the module’s name is long. This only imports the module’s name into the namespace, minimizing conflicts.

Here’s an example:

import datetime as dt
print(dt.date.today())

Output:
YYYY-MM-DD

Here, we import the datetime module but give it the alias dt. We can then call functions like date.today() using the shorter dt prefix, which is particularly useful for frequently used modules.

Method 4: Importing a Function with an Alias

Similar to aliasing a module, a function can be given an alias. This is useful if the function has a long name or if you want to avoid name conflicts with other functions.

Here’s an example:

from datetime import datetime as dt
print(dt.now())

Output:
YYYY-MM-DD HH:MM:SS.mmmmmm

In this snippet, we import the datetime class from the datetime module with an alias dt. This allows us to call dt.now() to get the current date and time.

Bonus One-Liner Method 5: Importing a Function Inline

For quick, one-time uses, you might opt to import a function directly inline. Be aware that this approach is unconventional and typically frowned upon as it can reduce code readability.

Here’s an example:

print(__import__('math').sqrt(16))

Output:
4.0

This example uses Python’s built-in __import__ function to import the math module and immediately calls the sqrt function on the number 16. This inline import is concise, but can be confusing for maintenance and readability.

Summary/Discussion

• Method 1: Single Function Import. Efficient and clear. Limited to one function at a time.
• Method 2: Import All Functions. Convenient for multi-use. Risk of clutter and conflicts.
• Method 3: Module with Alias. Simplifies and shortens code. Adds an extra step for readers.
• Method 4: Function with Alias. Personalizes function names. Can be initially confusing.
• Method 5: Inline Function Import. Compact for one-offs. Poor for readability and standard practices.