I have a directory that stores all the .py files.

bin/
   main.py
   user.py # where class User resides
   dir.py # where class Dir resides

I want to use classes from user.py and dir.py in main.py.
How can I import these Python classes into main.py?
Furthermore, how can I import class User if user.py is in a sub directory?

bin/
    dir.py
    main.py
    usr/
        user.py

Python 2

Make an empty file called __init__.py in the same directory as the files. That will signify to Python that it’s “ok to import from this directory”.

Then just do…

from user import User
from dir import Dir

The same holds true if the files are in a subdirectory – put an __init__.py in the subdirectory as well, and then use regular import statements, with dot notation. For each level of directory, you need to add to the import path.

bin/
    main.py
    classes/
        user.py
        dir.py

So if the directory was named “classes”, then you’d do this:

from classes.user import User
from classes.dir import Dir

Python 3

Same as previous, but prefix the module name with a . if not using a subdirectory:

from .user import User
from .dir import Dir

I just learned (thanks to martineau’s comment) that, in order to import classes from files within the same directory, you would now write in Python 3:

from .user import User
from .dir import Dir

In your main.py:

from user import Class

where Class is the name of the class you want to import.

If you want to call a method of Class, you can call it using:

Class.method

Note that there should be an empty __init__.py file in the same directory.

You can import the module and have access through its name if you don’t want to mix functions and classes with yours

import util # imports util.py

util.clean()
util.setup(4)

or you can import the functions and classes to your code

from util import clean, setup
clean()
setup(4)

you can use wildchar * to import everything in that module to your code

from util import *
clean()
setup(4)

In python3, __init__.py is no longer necessary. If the current directory of the console is the directory where the python script is located, everything works fine with

import user

However, this won’t work if called from a different directory, which does not contain user.py.
In that case, use

from . import user

This works even if you want to import the whole file instead of just a class from there.

To make it more simple to understand:

Step 1: lets go to one directory, where all will be included

$ cd /var/tmp

Step 2: now lets make a class1.py file which has a class name Class1 with some code

$ cat > class1.py <<\EOF
class Class1:
    OKBLUE = '\033[94m'
    ENDC = '\033[0m'
    OK = OKBLUE + "[Class1 OK]: " + ENDC
EOF

Step 3: now lets make a class2.py file which has a class name Class2 with some code

$ cat > class2.py <<\EOF
class Class2:
    OKBLUE = '\033[94m'
    ENDC = '\033[0m'
    OK = OKBLUE + "[Class2 OK]: " + ENDC
EOF

Step 4: now lets make one main.py which will be execute once to use Class1 and Class2 from 2 different files

$ cat > main.py <<\EOF
"""this is how we are actually calling class1.py and  from that file loading Class1"""
from class1 import Class1 
"""this is how we are actually calling class2.py and  from that file loading Class2"""
from class2 import Class2

print Class1.OK
print Class2.OK
EOF

Step 5: Run the program

$ python main.py

The output would be

[Class1 OK]: 
[Class2 OK]:

Python 3

Same directory.

import file:log.py

import class: SampleApp().

import log
if __name__ == "__main__":
    app = log.SampleApp()
    app.mainloop()

or

directory is basic.

import in file: log.py.

import class: SampleApp().

from basic import log
if __name__ == "__main__":
    app = log.SampleApp()
    app.mainloop()

from user import User 
from dir import Dir 

If user.py and dir.py are not including classes then

from .user import User
from .dir import Dir

is not working. You should then import as

from . import user
from . import dir

I’m not sure why this work but using Pycharm build from file_in_same_dir import class_name

The IDE complained about it but it seems it still worked. I’m using Python 3.7

Just too brief, Create a file __init__.py is classes directory and then import it to your script like following (Import all case)

from classes.myscript import *

Import selected classes only

from classes.myscript import User
from classes.myscript import Dir

to import from the same directory

from . import the_file_you_want_to_import 

to import from sub directory the directory should contain

init.py

file other than you files then

from directory import your_file

Python3

use

from .user import User inside dir.py file

and

use from class.dir import Dir inside main.py
or from class.usr import User inside main.py

like so