Learn to use the ?import?, ?from?, and ?as? commands
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Importing modules is a critical skill when learning Python. To keep the language lightweight and fast, only a small core is available by default in any given Python script ? you as the author are expected to then import whatever else is needed.
There are three main commands when adding modules to your Python code: import, from, and as.
We?ll go over each of these, but first let?s define what it is we?re actually importing.
What Can You Import?
The terminology can get confusing, especially when learning from multiple sources, so here?s a quick list of what can be imported and what they?re called.
- Module: simply a file with a .py extension.
- Package: a directory containing an __init__.py file and normally other modules.
- Built-in Module: A module that is natively installed with Python.
- Object: Anything inside a module/package that can be referenced such as a class, function, or variable.
Don?t get too caught up in the terminology. Just know that we?ll predominately be importing built-in modules or downloaded packages. Since object is such a multipurpose term, I?ll refer to them as components.
To download and install packages, use pip. This command line tool installs publicly available Python packages. For the examples below, we?ll only use built-in modules to ensure you can follow along.
How To Import in Python
Okay, now for the good stuff.
As mentioned earlier, there are three commands that can be used when loading modules into your code. Of the three, only import is absolutely required; the other two are optional depending on circumstance.
We?ll start with the simplest command, importing an entire module.
import mathprint(math.ceil(3.4)) # 4print(math.floor(3.4)) # 3
Just the command import and the module name? Super easy. Remember, if you?re importing a module that is not native to Python core installation, then ensure it has been properly downloaded.
Now, while this command is very straightforward, it isn?t very efficient. We may only need a small portion of the module, in fact that is often the case.
To be more specific, we?ll use the from command to specify our module, then the import command to explicitly list the components we need.
from math import ceil, floorprint(ceil(3.4)) # 4print(floor(3.4)) # 3
So now we?re more efficient in terms of what we?re importing, but you may want to simplify the reference or provide context to a component?this is where the as command comes into play.
To locally rename a component, follow up the import command with as and specify the new name. Now we can more clearly reference the component in our local namespace.
from datetime import datetime as dtprint(dt.now()) # 2020-03-29 01:43:03.170480
Conclusion
A well planned import should only bring in what is needed. Taking a few seconds to plan this out will save you time in the long run. Modifying imports for existing code most likely mean updating references and statements in the body of your program as well.
There is more to mastering Python module imports, but this will get you started and cover 90% of your import commands.
