In order to have a really solid foundation in Python, it's important to understand the Python execution model. By this, we mean the rules defining precisely when function definitions and other important events occur during module import and execution. To help you develop this understanding, we'll focus on the def
keyword since you're already familiar with it. Once you have an understanding of how def
is processed by Python, you'll know most of what you need to know about Python's execution model.
What's important to understand is this: def isn't merely a declaration, it's a statement. What this means is that def
is actually executed at runtime along with the rest of the top-level module-scope code. What def
does is to bind the code in the function's body to the name following def
. When modules are imported or run, all of the top-level statements are run, and this is the means by which the functions within the module
namespace are defined.
To reiterate, def
is executed...