PrintThe form of the “import” command that you definitely should already know is
import <module name>
e.g.,
import arcpy
What happens here is that the module (either a module from the standard library, a module that is part of another package you installed, or simply another .py file in your project directory) is loaded, unless it has already been loaded before, and the name of the module becomes part of the namespace of the script that contains the import command. As a result, you can now access all variables, functions, or classes defined in the imported module, by writing
<module name>.<variable or function name>
e.g.,
arcpy.Describe(…)
You can also use the import command like this instead:
import arcpy as ap
This form introduces a new alias for the module name, typically to save some typing when the module name is rather long, and instead of writing
arcpy.Describe(…)
, you would now use
ap.Describe(…)
in your code.
Another approach of using “import” is to directly add content of a module (again either variables, functions, or classes) to the namespace of the importing Python script. This is done by using the form "from … import …" as in the following example:
from arcpy import Describe, Point , … ... Describe(…)
The difference is that now you can use the imported names directly in our code without having to use the module name (or an alias) as a prefix as it is done in line 5 of the example code. However, be aware that if you are importing multiple modules, this can easily lead to name conflicts if, for instance, two modules contain functions with the same name. It can also make your code a little more difficult to read since
arcpy.Describe(...)
helps you or another programmer recognize that you’re using something defined in arcpy and not in another library or the main code of your script.
You can also use
from arcpy import *
to import all variable, function and class names from a module into the namespace of your script if you don’t want to list all those you actually need. However, this can increase the likelihood of a name conflict.