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Cannot execute pip after changing virtualenv folder name

So previously I named my virtual environment "test". After that, I changed it to "testt", and after that I can't access pip commands anymore and it gives me the following error:
Fatal error in launcher: Unable to create process using '"C:\coding\test\test\Scripts\python.exe" "C:\coding\test\testt\Scripts\pip.exe" ': The system cannot find the file specified.
How can I fix this?

You should never rename a virtual Python environment. When creating the virtual environment, the path is hardcoded in several places (see the Scripts/activate* scripts for example).
You could try to replace the hardcoded paths in all files, but I'm not sure how good this works and if this changes between (Python/venv) versions.
Best thing to do is just remove the old virtual environment and create a new one.
If you're using a requirements.txt file, this as as easy as:
py -3.10 -m venv new_env
new_env\Scripts\python.exe -m pip install -r requirements.txt
(example commands are for Windows and Python 3.10, but are similiar for Linux and/or other Python versions)
If you didn't use a requirements.txt file, you could run pip freeze before removing the old virtual environment to see which modules you had installed.
Side note: this method has the advantage that you're actually verifying that your environment is well documented (i.e., the requirements.txt is up-to-date) and that you can reproduce it. This will make it easier to repeat this process in the future (e.g. on another computer) as well.

How to run python project on Windows

I'm a mobile dev, no experience with backend environment. I'd appreciate some steps to config my Windows to run python projects, like this one: https://github.com/avilash/TikTokAPI-Python
I can't figure out how to config, run, and test those methods that are described. I assume it should be an IDE for python, but not sure which one is good for Windows, and how ton config it to run a project like this.
On mobile it's a lot easier, just download project, import in the IDE and run it. Any best practices for experienced devs are appreciated!

install python on your pc, then do pip3 install -r requirement.txt . I personally prefer vscode. Its the best with required extension installed, or if you are the newbie and you want to learn python, then don't install extension.

Download the standard Python distro from here https://www.python.org/downloads/. I would stick with versions 3.6 or 3.7 for now for stability and compatibility reasons.
Run the installer, the default installation path will be something like C:\Program Files\Python3X\. Since you're installing it for the first time, it will be your only installation, so you can choose during the install to set your environment variables (typically including PATH and PYTHONPATH) to point to this installation as the default one.
Create your project folder anywhere you like, where you can put your .py scripts. You can then cd into the folder in the command line and run any scipt like this python myscript.py (or if you haven't set the default env vars C:\Program Files\Python3X\python.exe myscript.py).
This is the bare minimum you need to be able to run Python projects.
To install the package you mentioned, in the command line type pip install git+https://github.com/avilash/TikTokAPI-Python (or C:\Program Files\Python3X\Scripts\pip.exe install git+https://github.com/avilash/TikTokAPI-Python). This will work because the project has a setup script (setup.py). Note that this will install it into the Python installation folder and you will NOT be able to modify it. If you want to be able to do development on it, clone it into a separate folder, navigate into it and install in 'dev' mode from the current folder using pip install -e . (note the dot!)
For the IDE, you can use VS Code if you're already using it, just install the Python extension. If you're more into IntelliJ, you can then use PyCharm which will have the familiar interface but it's a separate IDE. Both are similarly good in terms of features and maturity.
Other notes you can find useful at the beginning:
If you install multiple Python installation in different places, they are pretty much self-contained and defined by their installation path, but of course the one for which you will select to set the environment vars during installation will be the default one. If you want to run the pip command for a specific installation, then you will have to use C:\Program Files\Python3X\python.exe -m pip install ....
pip is Python package manager, typically you can install anything available on https://pypi.org/ with just pip install pandas for example.
You can check all packages installed using pip list. Since pip itself is also just a Python package, it will always be in the list as it's installed by default when you install Python.

How do I test out changes to a python library pulled through git?

I have a python library that I am wanting to help out with and fix some issues. I just don't know how to test my changes given the complexity of how python/pip installs libraries.
I have the library installed with pip and I can run python code connecting to the library by doing an "from import *". But now that I want to make changes to it I pulled the code with git and plan to branch to work on my changes. That's fine. I will then do a pull request to merge any changes given tests pass.
But after I make a change, how do I integrate my changes into python to test out the changes I made with the library? Can pip install my custom/modified version of the library?
I have looked around and haven't successfully found an answer to this but perhaps I'm not looking in the right spot.

Can pip install my custom/modified version of the library?
Yes.
There are various ways of approaching this question. A common solution is the use of Python virtual environments. This allows you to create an isolated Python environment that does not share the same packages as your system Python install. You can then install things into it (such as your modified Python library) to test it out.
To get started, you need the virtualenv tool. This is probably available as a package for your distribution, but you can also install it using pip. Once you have it, you can run in the same directory as your code:
virtualenv .venv
This creates a virtuelenv named .venv. You can call it anything you want, but naming it .venv (or anything starting with a .) means it won't clutter up the output of ls in your workspace.
Next, you need to activate the virtualenv:
. .venv/bin/activate.sh
This modifies your $PATH to place the virtualenv at the front of the list of directories. Now when you type python or pip, you'll be using the virtualenv version.
If your code has a setup.py file, you can install it like this:
pip install -e .
The -e means you want to perform an "editable" install, which means python will use the code "in place", and any changes you make will be immediately visible to the code you use for testing.
When you're done, you can run:
deactivate
This will remove the changes that activate made to your environment.
For more information:
Pipenv & Virtual Environments discusses a higher level tool for managing virtual environments.
Virtualenvwrapper is another take on a higher level management tool.

How can I manage mutiple python in Ubuntu16.04?

  In my Ubuntu16.04, there are python 2 and python 3 default. In addition, i have installed anaconda too. I am sucked by the 'python' cmd. Every time i use pip or pip3 install, I don't know where the package install, python2 or python 3? And I use conda install to install anaconda package. I also use anaconda env to manage different virtual env. But I think it mix with my local Python 2 and 3.
  For example, in directory /usr/bin, I found many soft links like this:
   When i try 'python' cmd, it just confuse me！
   Why python3m are local, shouldn't it be anaconda? Why python3 are anaconda, shouldn't it be local? Then I found that if I use ./python2 or ./python3, I found it is correct now!
  So I know it is caused by environment variables. I echo $PATH, Found it like this: /home/kinny/.pyenv/shims:/home/kinny/.pyenv/bin:/home/kinny/anaconda3/bin:/home/kinny/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/opt/ant/bin:/snap/bin:/opt/maven/bin:/usr/lib/jvm/java-8-oracle/bin
   I have used update-alternative --config python to configure default python, but it doesn't work! It sames mixed with each others.
   Now I just want to install tensorflow 0.11 in local python3, because in anaconda it is 0.10 version by default. So how can I change this. I just want to use python python3 and python3m represents python2.7 python3.5 and anaconda python respectively, How can I do that! use pip and pip3 for local python2 and python3 respectively!

I ran into a similiar problem when setting up PyCharm Edu to work with Anaconda. I found that I had several versions of Python installed and it was very hard to keep track of which version the IDE was referencing. My CS professor gave me the advice of simply removing the versions of Python I didn't frequent. I now just have Anaconda installed; and use the Anaconda Prompt as my Python console. I also rely on PyCharm's IPython for the developer console. However, if you still want differing versions of Python installed (say your doing QA testing for older devices); there is the really helpful command: which python. When entered into the python console or Anaconda Prompt: which python will display the directory associated with the currently executing Python Shell. This enables you to better keep track of to what particular python.exe the current window is referring to.

Follow up to the comments mentioning using virtualenv and virtualenvwrapper.
Here are the official docs and a good blog post to follow for getting started using virtualenv's is here:
https://virtualenv.pypa.io/en/stable/installation/
http://virtualenvwrapper.readthedocs.io/en/latest/install.html
http://exponential.io/blog/2015/02/10/install-virtualenv-and-virtualenvwrapper-on-ubuntu/
Also, once you are setup you can create virtualenv's specifying which python installation you want to use.
which python3
returns
/usr/bin/python3
Then create a virtualenv with that python path. Where example_env is the name of the virtualenv.
mkvirtualenv -p /usr/bin/python3 example_env
Then activate the virtualenv using virtualenvwrapper.
workon example_env
Finally, install tensorflow and other dependencies with pip.
pip install tensorflow

the which command is very useful for finding the path to the executable that is first in your path. Zsh also has the where command, which will show you all instances of the given executable that show up in your path. For managing different python versions, you have a lot of options. The easiest for most people tends to be anaconda, using conda environments. The installer will ask you to add some stuff to your .bashrc file, which will then make anaconda's binaries come first in your path. Anything else you run after the .bashrc gets sourced after that, will then use that first, including PyCharm. For graphical desktop apps to pick up the change, you may need to log out and back in again. If you only need one version each of python 2 and python 3, you can just use the ones available via apt. Depending on your Ubuntu version, Python 2 is definitely installed by default as it is used by many system utilities, including apt itself. Some newer versions may also install python 3 by default, but I do not remember for sure. Another option is to install the versions of python you need in an alternate location, such as /opt/python/<version> and then using environment-modules (installed via apt install environment-modules) or Lmod to control which versions are being used, but that may or may not be easy/convenient to use with a desktop application such as PyCharm.
for TensorFlow, 1.11 is available in anaconda, but I don't remember if it's in the default channel or not.

Confused about Python installations, module installation, and interpreter

So yesterday I had to create a virtualenv in order to be able to install Python modules that wouldn't install thanks to OS X El Capitan's new SIP. I thought I did everything right, but today I'm reaching a different conclusion. I hope I can be clear about it.
my python custom install is at myname/learnp/imdb_module, this is where I created it with virtualenv. Edit: I later moved it to myname/learnp/ayr2/imdb_module.
However, when I try to run the interpreter, it seems to always default to the Python that is in Library or something along these lines. I found out about this because a certain module that I managed to install in this custom python env wouldn't import, when I checked what modules I have, it wasn't the same as what I expected.
Furthermore, it seems that ALL other modules that I wanted to install on the CUSTOM virtualenv were installed on the main python env, and that I wasn't installing those modules on the custom env all along.
Excuse me, but I'm very confused right now.
I know how to create a virtual env
I know how to activate it (it appears to the right on Terminal line)
I don't know how to install modules to my virtual env
I don't know how to make the interpreter run from the virtual env so I can do python operations that are only possible by using custom env modules
Any advice is much appreciated!
Update:
Followed Will Hogan's answer for troubleshooting,and I think something weird is happening, quoting my comment to his answer:
HI, thanks for taking the time to answer. This is basically the way I understood this. However, let me attach a screenshot: http://i.imgur.com/DfpngJq.jpg . Am I right to assume something is wrong here? My prompt is changed with the virtualenv named "imdb_module", but when I type in which python it doesn't list ayr2/imdb_module/bin but rather a folder with the path usr/bin/python, which if I understand correctly is the "default" environment.
And not if this helps in any way, but echo $PATH when (imdv_module) appears to the right of the prompt, gives this (I redacted my name): /Users/REDACTEDNAME/learnp/imdb_module/bin:/Library/Frameworks/Python.framework/Versions/3.4/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin

While creating the virtualenv you should see it installing setuptools and pip:
$ virtualenv testvenv
New python executable in testvenv/bin/python2.7
Also creating executable in testvenv/bin/python
Installing setuptools, pip...done.
After ensuring the virtualenv is activated you should see your prompt change:
$ . ./testvenv/bin/activate
(testvenv)$
Now you can confirm the paths to python and pip, which should be in the virtualenv:
(testvenv)$ which python
/private/tmp/testvenv/bin/python
(testvenv)$ which pip
/private/tmp/testvenv/bin/pip
If you aren't seeing the python and pip locations as being under the virtualenv's directory, then the virtualenv has not been activated.
I would also ensure that, if you're executing the .py file directly (and not with "python foo.py"), that your shebang line uses:
#!/usr/bin/env python
Or even the full path to the virtualenv's python, e.g.:
#!/tmp/testvenv/bin/python
As opposed to, say:
#!/usr/bin/python
The first will search in the current environment, which will be set by the virtualenv activation. The second explicitly points to the virtualenv's `python'.