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Pip upgrading arcgis completely broke pip

Overview: While running Python 3.6, after upgrading my arcgis package, scripts no longer recognizes many packages and pip itself completely broke, making it impossible to upgrade or uninstall any packages.
Background Info: Fairly recently, when I run a particular program of mine, I have been seeing a deprecation message connected to the arcgis package. So, I upgraded the arcgis package to see if it fixed it. It seemed to install correctly but then when trying to run my program, I'd get errors for other packages, like folium or requests. I then tried upgrading Python and initially, it worked. I used pip to install pandas and requests but right after I installed arcgis, everything broke again. So then when trying to uninstall arcgis (or do anything else pip related) I get this error:
FileExistsError: [WinError 183] Cannot create a file when that file already exists: 'C:\Users\myuserpath\AppData\Local\.certifi'
I've uninstalled Python but it doesn't change anything. pip install any package results in this error. I tried reverting back to Python 3.6 but the installer wasn't available from the python site, only 3.9.
What could have been changed or affected by this arcgis installation?

There seems to be two primary issues you're dealing with. The first is as #BoarGules mentioned, that arcgis does a 'full' install with all its dependencies and that could be causing problems. Secondly, the newest requests library seems to have some issues as well, at least from what I've experienced. So let's get started fixing all this.
There's probably a few different ways to fix this, so this is just one of the many. First, uninstall python and delete the python folder from your AppData folder - in your case, it would be the Python 3.9 folder. Re-install Python and check your site-packages folder making sure it only contains the default Python packages. Open up a command prompt and do a pip install of something basic, like pandas. If that goes well, then the first hurdle is over.
When it comes time to install arcgis again, you'll want to use this instead
pip install arcgis --no-deps
this will prevent the doubling up of any of the packages or whatever seems to be happening. You will need to then also install these:
pip install ujson
pip install requests_ntlm
Next, when you come to installing requests, use an older library, like this one:
pip install requests==2.20.0
That should get things back up and running.

Use pip with non-standard Python installation (non-root installation)?

I'm trying to get up and running with Python 3.5.2 and various packages on a server I work on, but don't have root privileges for. I installed Python to my home, and that seems to be working. I'm trying to set it up so I can install packages to that Python installation (ie ~/lib/python3.5/site-packages) via pip, but I cannot get it working.
Even after adding ~/lib/python3.5/site-packages to $PYTHONPATH, no luck.
Running pip install pandas, I get the error /usr/local/bin/python3.5: bad interpreter: No such file or directory , so it's still looking in the wrong spot. It should be looking at ~/bin/python3.5. Setting an --install-option="--prefix= argument doesn't change the problem.
Is this possible to do?

Try this:
pip3 install --user "library name"

Installing shapefile / shapelib not found via conda or pip

I am trying to read shapefiles to view suburbs in a city following this tutorial using windows 8, Anaconda and iPython.
I tried "conda install shapefile" and "pip install shapefile" in command prompt, both returning "Error: No packages found matching: shapefile".
Besides that I tried adding it manually following these links [1]How to import a module given the full path?
[2]Import python module NOT on path. However I am getting permission errors which suggests I am not importing them correctly anyway.
Any suggestions on how to proceed or best practices are appreciated.

try
pip install pyshp
in your cmd.
that is the name of you library as far as I can see, see https://pypi.python.org/pypi/pyshp
conda only works for these http://docs.continuum.io/anaconda/pkgs.html packages.
For the ones not in the list you need to use pip install. It can be confusing as the name of the library on pypi (this is where pip goes to download it) is often, but not always the same as the import name, so if conda and pip don't work, first try to google to make 100% sure that your library is not on pypi, because most respectable libraries are...

Installing python packages in nitrousio

I've just started trying to use Nitrous.io. I've made a box with python, and am trying to use pip to install a python package called praw.
It downloads all of the information fine, but on running the install script, I get an error stating that it could not create a file due to permission restrictions in the /usr directory. Is there any way to get around this as I need the package for my application to work properly.

You could try pip install --user praw
https://pip.pypa.io/en/latest/user_guide.html#user-installs

how to install virtualenv and/or pip

Someone please tell me I'm not crazy, becuase I really feel like I am right now.
Ok so, I'm trying to setup a webapp with python and django using heroku, but I've hit quite an odd obstacle.
It wants me to setup a virtualenv using the command $ virtualenv venv --distribute, which is all well and good except:
yeh, so naturally I googled how to install virtualenv and I found this:
But, of course:
So I continued my search by trying to find out how to install pip and I found this:
Aaaaaaand that's when I completely lost my marbles because apparently you need to install pip to install virtualenv to install pip. (maybe not, but that's why I'm a noob and I need help).
But then I took another look at the vitualenv installation guide, and found that I could download it and install it manually, so I extracted all the files from the downloaded archive into my python33 folder and used setup.py install. And I got this:
So I changed the line in that file to except ValueError as e and I got another error from a different python file in that same folder so I reverted the change I made and decided that it probably was not a good idea to meddle with those scripts.
Please, any help at all to do with setting up a free server with python and django would be greatly appreciated. Furthermore, I am sorry if my question is stupid, or incorrectly tagged.

You are following install guides for linux. You should try to find an install guide for pip and virtualenv on windows. First install pip systemwide and then use pip to install virtualenv systemwide. Then start using virtual environments.
Start with How to install pip on W$ and Python and virtualenv on W$. An alternative is the Hitchhiker's guide to python.
Edit
As Ron Elliott states in the comments,
you'll need to point your path to C:\Python2x\Scripts or C:\Python3x\Scripts in order to pick
up easy_install and pip as well as any other script executables
installing to that directory.

But then I took another look at the vitualenv installation guide, and
found that I could download it and install it manually, so I extracted
all the files from the downloaded archive into my python33 folder and
used setup.py install.
You downloaded the package and run setup.py install in wrong folder, that's why it didn't work.
You should:
Download the archive virtualenv-1.10.tar.gz to a Downloads folder (or where ever you want)
Extract it, you will have a folder name virtualenv-1.10
Go to (cd) the extracted folder
Run command: python setup.py install
Anyway I would recommend installing setuptools and pip first, then you can install virtualenv from pip: pip install virtualenv.