Develop Reference

Python Libraries installing to Python 2.7 by default

I recently shifted to a Macbook. I installed Python 3.8 and installed Pyperclip using pip install pyperclip in the terminal, which was successful. When I tried to import it in IDLE shell, I get the error
ModuleNotFoundError: No module named 'pyperclip'.
On looking around I found that pyperclip has been installed in-
/Users/aamodpant/Library/Python/2.7/lib/python/site-packages/pyperclip
I did not install Python 2.7 but it must be required for macOS, so I don't want to delete it. How do I change the "default" version of Python for installing new libraries?

Use :
python3 -m pip install pyperclip
This will install the package for python3.

You can reinstall or upgrade pyperclip using sudo:
pip3 install -U pyperclip
Also, run your script using python3 instead of just python:
python3 script.py
The best is to use alias, as this answer describes changing default Python version in Mac can cause multiple issues.
alias python=python3
alias pip=pip3
The answer you are probably looking for is You should not change this.
Otherwise, you may like to set Python 3 as default, there are many ways to do it. But do it with caution as the guides suggest below.
The official documentation: Using Python on a Macintosh, some well described very good guides: The right and wrong way to set Python 3 as default on a Mac, Installing Python 3 on Mac OS X.

Installing packages in Python 3.8 - pip fatal error, seems to be stuck on 3.6 somehow

I am running Python 3.8.3. Previously I had Python 3.6 installed.
When I try to install by pip e.g.
pip install requests
I get the error
Fatal error in launcher: Unable to create process using '"c:\users\myname\appdata\local\programs\python\python36\python.exe" "C:\Users\MyName\AppData\Local\Programs\Python\Python36\Scripts\pip.exe" install requests'
Uninstalling Python 3.6 did not resolve this. I also tried reinstalling pip from https://pypi.org/project/pip/#files.
How can I get pip working again so I can install packages again?
On a side note, the reason I installed 3.8.3 in the first place instead of continuing with 3.6 was that Windows opened its app store any time the python command was used in PowerShell. I figured I might as well download the new version, since at the time I saw no reason to fight it. Still, it would be nice to know how to stop Windows from commandeering this.

If typing python in your command prompt opens python 3.6 then try py -3 or another possible PATH variable you have set for python 3.8
then to use pip for just that python version do the following command
[PATH VARIABLE] -m pip install [py-package]
e.g.
python -m pip install requests

When you are runing pip install requests, it runs the first pip it finds on th path. You can see from the error message, that it is using c:\users\myname\appdata\local\programs\python\python36\python.exe, so you are not really installing anything for Python 3.8.
If running python on your computer runs Python 3.8, then I suggest using this option to run pip:
python -m pip install requests
And if you have to enter full path to start python3.8, than do that:
/full/path/to/python.exe -m pip install requests

Pip inside virtual environment throws error

I am using virtual environment in python. When I use pip list command or any command to install packages it throws an error.
from pip._internal.distributions import (
ModuleNotFoundError: No module named 'pip._internal.distributions'
When I check the version pip -V inside venv it shows the version of pip (i.e. no error, working great). But, it is not working in any other commands. Please ask if I did not make it clear.
Thank you!!!
EDIT:-
I am using Windows 10 Pro. I installed python from their official website of version 3.8.1 using the windows installer. And, my pip version is 20.0.2 I installed pip by adding get-pip.py in bin file. I think there should not be any problem.

Is there a solution to why I can't pip install any python modules past 2.7?

I can't install any python modules that require python 2.7 or later. I have uninstalled everything that Mac would let me that was related to python 2, and I run everything on python 3. I am completely lost. I am on Mac and whenever I try to install a module(like praw) this pops up.
I used the command
pip install praw
Collecting praw
Using cached https://files.pythonhosted.org/packages/41/89/94c1ec81a05536e2c2a1dc2e8f5402c8ad65963f28948bf41c64621e238b/praw-6.5.0-py2-none-any.whl
ERROR: Package 'praw' requires a different Python: 2.7.16 not in '>=3.5' ```

Welcome to Stack Overflow Malachi! I believe you're looking for the command pip3 (pip3 install praw) to install Python 3 packages through pip. If you open your terminal and type man pip to get the manual page, there is a line that says:
pip is the command to use when installing packages for Python 2, while pip3 is the command to use when installing packages for Python 3.

Looks like the most recent version of praw requires Python 3.5 or greater.
The last version that supported Python 2.7 was praw 5.4.0. If you're still using Python 2.7 and need this package, try running
pip install praw==5.4.0
If you're using Python 3.x, check to see if you're using the right version of pip. If you have both Python 2 and Python 3 installed on your system, you'll likely need to install system wide packages using pip3 instead if pip. In this case, try running
pip3 install praw
Alternatively, if you're targeting a specific Python interpreter (e.g. python3.7, python3.8, etc), and want to be certain that you are using the correct pip executable for your interpreter, you can run pip as a Python package via
python3 -m pip <args>
where python3 can be replaced by any interpreter path.

Installing Python Libraries When Multiple Versions of Python Exist

When I run python -V from terminal, I see that Python 2.7.10 is installed. I want to keep this as the "global" version as OSX utilizes it.
When I run Idle, I see that Python 3.6.0 is running. How do I install libraries to this version of Python?
For example, if I run pip install bs4, the library is installed here beautifulsoup4 in /Library/Python/2.7/site-packages/beautifulsoup4-4.5.3-py2.7.egg - which is obviously Python 2.7.
So when I run my script from Idle, I get the following error:
ModuleNotFoundError: No module named 'bs4'

You want to use virtualenv. It sounds like you have two versions of Python installed and you need to focus on one while being able to manage the packages in each. Virtualenv will do this for you.
First install virtualenv (https://virtualenv.pypa.io/en/stable/),
Second run it specifying the version of python you want as so: `virtualenv -p /usr/bin/python2.6
Third you can use pip to install packages directly into this environment. This increases the amount of disk space you need, but will allow you greater control over your code.

When you have two versions of python, you will need to specify which version of python you would like to run. You can do this with the activate command. For example:
activate python3
Once you have activated the python 3 environment, you can then run pip:
pip3 install bs4
which will install the beautiful soup library in your python 3 environment.

Another answer was found here: https://stackoverflow.com/a/4910393/1580659
pipVERSIONNUMBER install will install the library to the correct version of Python.
$ pip2.6 install otherpackage
$ pip2.7 install mybarpackage