Python for Entrepreneurs Transcripts
Chapter: Appendix: Python language concepts
Lecture: Concept: Imports and importing modules
Login or
purchase this course
to watch this video and the rest of the course contents.
0:01
Packages and modules must be imported in Python before they can be used.
0:06
It doesn't matter if it's in external package of the package index,
0:09
in module from the standard library or even a module or package
0:12
you yourself have created, you have to import it.
0:16
So code as it's written right here likely will not work,
0:20
you will get some kind of NameError, "os doesn't exist, path doesn't exist".
0:23
That's because the os module and the path method contained within it have not been imported.
0:29
So we have to write one of two statements above,
0:33
don't write them both, one or the other.
0:35
So, the top one lets us import the module and retains the namespace,
0:39
so that we can write style one below, so here we would say os.path.exist
0:44
so you know that the path method is coming out of the os module.
0:47
Alternatively, if you don't want to continue repeat os.this, os.that,
0:52
and you just want to say "path", you can do that by saying this other style,
0:56
from os import path.
0:58
And then you don't have to use the namespace,
1:00
you might do this for method used very commonly
1:02
whereas you might use style one for methods that are less frequently used.
1:07
Now, there is the third style here, where we could write "from os import *",
1:10
that means just like the line above, where we are importing path,
1:14
but in fact, import everything in the os module.
1:17
You are strongly advised to stay away from this format
1:19
unless you really know what you are doing, this style will import and replace
1:24
anything in your current namespace that happens to come out of the os.
1:28
So for example, if you had some function that was called register,
1:33
and maybe there is a register method inside os module,
1:37
this import might erase your implementation, depending where it comes from.
1:41
So, modules must be imported before you use them,
1:44
I would say prefer to use the namespace style, it's more explicit
1:48
on where path actually comes from,
1:50
you are certain that this is the path from the os module,
1:52
not a different method that you wrote somewhere else
1:54
and it just happens to have the same name.
1:56
Style two also works well, style three- not so much.
