How to write PYTHONPATH correctly?

Question

Python

Hello.
I installed the package from the sources, everything is OK:

...
Installed /usr/local/lib/python3.5/dist-packages/keras_segmentation-0.2.0-py3.5.egg
Processing dependencies for keras-segmentation==0.2.0
Finished processing dependencies for keras-segmentation==0.2.0
(base) [email protected]:~/image-segmentation-keras$ python3
Python 3.7.3 (default, Mar 27 2019, 22:11:17) 
[GCC 7.3.0] :: Anaconda, Inc. on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import keras_segmentation
Using TensorFlow backend.
>>> exit()

Closed the terminal. Opened:

(base) [email protected]:~$ python3
Python 3.7.3 (default, Mar 27 2019, 22:11:17) 
[GCC 7.3.0] :: Anaconda, Inc. on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import keras_segmentation
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'keras_segmentation'
>>>

Can you please tell me what could be causing this?
The path to the python is the usual:

>>> import sys
>>> sys.executable
'/home/user/anaconda3/bin/python3'

upd: the command helped:

(base) [email protected]:~$ sudo env "PATH=$PATH" python3 setup.py install

And how not to write env "PATH=$PATH" every time, why do you have to write this at all and where can you read about it?

Answer 1

> lib/python3.5
> Python 3.7.3
Doesn't the difference in versions bother you?