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I am receiving and import error when trying to import cv2 in python (Ubuntu 18.04)

First of all, thank you very much for reading.
Some days ago I installed Python3 (3.6.9) and opencv 3.4.10 in an Ubuntu 18.04 desktop system. I needed to downgrade opencv to 3.4.0 after some compilation problems (not related to python3), so I removed opencv 3.4.10 by using the sudo make uninstall order, and tested that it was uninstalled as if I tried importing it in python I got the following error:
libopencv_hfs.so.3.4: cannot open shared object file: no such file or directory
I thought installing 3.4.0 version would solve the problem but now that it's installed, when I try to import it in a python3 script I am getting the same error. I think this error must be related to the way python3 references the import files. I think it's still pointing to the uninstalled version of 3.4.10, but I can not find the way to change it.
Could someone please help me with this issue?
Thank you very much.
Andrés.

Using a virtualenv would resolve the issue. Check this out on how to use : Installing packages using pip and virtual environments
Once you're done installing requirements in the virtualenv, run your python script there only to use the specified versions.

Hello again and thank you for you answers.
I have been able to solve the problem. Thought I had uninstalled the previous version of opencv, there was still a cv2.sofile in my python virtual environment path, and it had not been replaced by the new cv2.so, so python tried to import the old one instead of the new one.
The old cv2.so (the one that was referenced when I imported cv2 in python) was here --> ~/.virtualenvs/cv/lib/python3.6/site-packages/cv2.so
The cv2.so I wanted to be used when imported was here --> /usr/local/lib/python3.6/site-packages/cv2/cv2.so so I replaced the one in the virtual environment path with the one in the lib directory and that did the trick :)

Python packages are imported on terminal but not on IDLE

So I am new in Python. I downloaded Anaconda (and Homebrew) and using Terminal on my Mac I confirmed that, say, Numpy is installed:
pip install numpy
to get as a result
Requirement already satisfied: numpy in ./anaconda/lib/python3.6/site-packages
Then opening Python within Terminal I can indeed import the package. The story is not the same once I open IDLE. So when I open it and try to import, say, Numpy I get the following message:
Traceback (most recent call last):
File "<pyshell#1>", line 1, in <module>
import numpy
ModuleNotFoundError: No module named 'numpy'
I guess there is something I do not know, I assume it is a common rookie problem. Can you help me with this?

Since your IDLE is using Python 3 you should use
pip3 install numpy
to get it installed for the correct Python. If you want to use your default installed Python (2.x) instead, IDLE is located at /usr/bin/. From your terminal you can open it with
/usr/bin/idle
this should have the numpy you installed with pip install numpy

See when you are working with Anaconda it creates its own virtual environment.
Now, If you are new in python on MAC then you might not familiar with Virtual Environment.
I suggest you to download python from the official website www.python.org
or Click here to directly download Python 3.6.2 on your MAC.
Then, Download Pycharm(The Best IDE for Python)
Download the community version for beginner and it is also free.
Pycharm Community Version -> Click Here
And do whatever you want and also must read about Virtualenv
According to me, Pycharm is better then Anaconda's Jupyter Notebook
Wish you good luck and show your creativity in python ! !

Erm... well it appears as though - since you have 2 versions on your computer - that it might be because it imported it into the other file path directory. Now, I've never worked with Mac, but I think if you just specify which pip you want to download from, it might work.
For example, on Windows:
C:\Python34\Scripts\pip.exe install numpy
or if you were doing it for 3.6, you would follow the path to the folder, find pip and install. So, I suggest to install the normal IDLE before any other platform built upon it just because it is easier to import modules and is not as bad to break like yours has.

There can be two issues -
You are using python 2 as a kernel for IDLE, since numpy is installed for python3.6. This will raise an error.
The issue is with anaconda's configuration with IDLE. Anaconda installs numpy in ./anaconda/lib/python3.6/site-packages. If IDLE uses systems default python instead of anaconda's. You will not be able to import numpy.
You can try running this snippet -
import sys
print('\n'.join(sys.path))
to track the location of python exactly.
One of the workaround that I can think of is -
create a virtual environment using anaconda. Something like
conda create -n py352 python=3.5.2 anaconda
and then fire IDLE from your terminal. Though I am not entirely sure, if this works for mac. If it doesn't, let me know the output of -
import sys
print('\n'.join(sys.path))

ImportError: No module named 'matplotlib'

Brand new to Python (typically program in MSDN C#) and I'm trying to make use of the matplotlib to generate some graphics from .csv files
I've downloaded & installed Python as well as Anaconda onto my Windows 10 machine, the versions are Python 3.5.2 and Anaconda 4.1.1
I open up the Python "notepad" interface and do
import matplotlib.pyplot as plt
plt.plot([1,2,3],[3,2,1])
plt.show()
but when I run the code I get the error:
ImportError: No module named 'matplotlib'
I've looked at some other posts for this but they all seem to be in regard to Mac OSX or Linux. Some have pointed to multiple installs of matplotlib, but I haven't turned up such a situation so far. What might be causing this, or how can I troubleshoot it?
**Edit:
The path returned to me from the import sys recommended in the comments gave me this response
['C:\Users\a.watts.ISAM-NA\Desktop',
'C:\Users\a.watts.ISAM-NA\AppData\Local\Programs\Python\Python35-32\python35.zip',
'C:\Users\a.watts.ISAM-NA\AppData\Local\Programs\Python\Python35-32\DLLs',
'C:\Users\a.watts.ISAM-NA\AppData\Local\Programs\Python\Python35-32\lib',
'C:\Users\a.watts.ISAM-NA\AppData\Local\Programs\Python\Python35-32',
'C:\Users\a.watts.ISAM-NA\AppData\Local\Programs\Python\Python35-32\lib\site-packages',
'C:\Users\a.watts.ISAM-NA\AppData\Local\Programs\Python\Python35-32\lib\site-packages\setuptools-26.1.1-py3.5.egg']

You essentially have 2 versions of python on your system - the standard one you downloaded and the one that ships with Anaconda. When you are running code in the IDLE you are using the standard version (in C:\Users\a.watts.ISAM-NA\AppData\Local\Programs\Python\Python35-32\python.exe) where matplotlib isn't installed which is why you are getting the error.
You need to use the Anaconda version (C:\Users\a.watts.ISAM-NA\AppData\Local\continuum\anaconda3\python.exe) that comes with the scientific stuff already setup. It looks like your system is using this one from the cmd so if you run scripts from there it should use the Anaconda version. If you want to use something more interactive you can also use spyder - the Anaconda version of the IDLE - or run jupyter notebook from cmd to get a browser based platform for interactive development

After installing NumPy in Python - I still get error: "no module named numpy"

I need to install and use the Python NumPy module (and then later the Pandas module) in order to process heavy data in Python.
I downloaded and installed ENTHOUGHT, but it wasn't what I wanted all that extra clutter of extra modules (which defeats the purpose of importing Python modules only as needed), but the uninstall did not work properly (i.e. it left garbage folders and ENTHOUGHT remnants all over my computer).
I have tried installing NumPy via EASY_INSTALL and PIP (two package managers if I understand correctly) - but with no success. Every time I try to run my program, I get the error: "no module named numpy".
I have searched the questions here and have tried to alter my ENVIRONMENT VARIABLE as per the following video, but again, no success:
https://www.youtube.com/watch?v=ddpYVA-7wq4
C:\Python34
...still the same error!
I downloaded Anaconda (with all its extra clutter and installed, but I don't like the development environment - I want my Vanilla Python IDLE to run Vanilla NumPy with no extra clutter modules...) and when I tried to again install Numpy I received a message that it was already installed with a path to:
C:\users\yoni\anaconda3\lib\site-packages
....so I ALSO added this PYTHONPATH to the ENVIRONMENT VARIABLE in hopes that it would now recognize where the NumPy installation was (currently with Anaconda3 - but I hoped to be able to import NumPy to my vanilla Python IDLE):
C:\Python34;C:\users\yoni\anaconda3\lib\site-packages
I don't find a clear answer - I see others have the same problem, and nothing is working for me. How can I finish this installation of NumPy so that it works for me when I do a simple import of module?

This is a temporary solution until you can resolve your path issue.
It will be environment specific.
import sys
sys.path.append('C:\users\yoni\anaconda3\lib\site-packages[PackageName]')
import PakcageName

Trouble in installing Basemap in matplotlib

I am trying to install Basemap, and beforehand I already have the prerequisite versions of Matplotlib, Python and Numpy working on my Mac. To install Basemap I am following the instructions in this website http://matplotlib.org/basemap/users/installing.html
I seemed to progress quite well with the steps, until the very end which is "Check your installation by running from mpl_toolkits.basemap import Basemap at the python prompt." I got "ImportError: cannot import name pyproj" from a line that reads "---> 30 from mpl_toolkits.basemap import pyproj".
Does anyone have any idea? Many thanks!

The compiled module could be accessible by python. To achieve that you should put the module into python path or you need to add the location of the module to PYTHONPATH environment variable.
To see the python installations paths you can write these lines to python shell:
import sys
for path in sys.path:
print(path)
The code will show the paths python is looking for modules.
After you compile the c library, you need to go to upper folder and run python setup.py install as it's said in the installation page. This will put python modules into one of your python paths.

I had the same problem installing basemap-1.0.7.
I found that the file
/usr/lib64/python2.6/site-packages/mpl_toolkits/basemap/init.py
had a reference to axes-grid1, but python lists only module axes_grid.
So I changed grid1 to grid and now basemap imports without error.

Had the same issue on OSX, found after much faffing that Basemap worked fine with a non-native version of python (for me 2.7.12 with everything under /opt/local/Library/Frameworks...) but not with the native version (for me 2.7.10 with most stuff under /System/Library/Frameworks... and Basemap under /Library/...). I did note also that under the native version there was already some mpl_tooklit content and without the permission to add Basemap there you end up with mpl_toolkit contents in multiple places. I wasn't sure if this was the problem specifically but as I said having it all under opt using non-native python was what solved this for me.