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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.

How to install pip packages to specific Python version?

I have Python 3.7 and Python 3.6. How to I chose to which version of Python I want my PIP packages?

On Linux the #jwodder answer is fine, but on Windows use the Python Launcher, which is normally installed by default. You specify the version of Python to launch as -X.Y, e.g.:
py -3.6 -m pip install ...

You use the version of pip that corresponds to the desired Python version. The most universally effective way is to run pythonX.Y -m pip install ..., where X.Y is replaced with the Python version number, though running just pipX.Y install ... may also work under some circumstances.

use python -m pip where python is the version of python you want to install to

I would suggest to use the newer and (now) recommended way of installing Python application dependencies: pipenv. You can consider pipenv to be the better pip (pip + virtualenv handling + proper depedency management). Using pipenv you create a Pipfile and you can specify the exact python_version you want to use in that file. Since I started using pipenv in my projects most headaches I had previously with Python dependency and version management are gone.

Which version of Pip to use with my Python installs?

Being new to Python, I'd love to clear up a few points that I couldn't get from reading various articles and tutorials.
After using Homebrew to install Python3, I noticed that it had installed both Python3 and Python3.4. I was also a little surprised that there are now three versions of pip on my machine too; pip, pip3 and pip3.4.
I created a new virtualenv and told it to use Python3, using the following command:
virtualenv -p /usr/local/bin/python3 mysite
I was also surprised that the version of Python that it installed in my VM was 3.4.
Is it safe to have these multiple version of Python and Pip hanging around on my machine?
Am I right to assume that I should take extra care to use the matching version of pip with Python, for example, pip3.4 with Python3.4?

Yes, it is safe. Python uses this naming like python3.4, python3.5 etc to differentiate between releases. python3 is a symbolic link to the current python3.x version. Pip follows the same convention.
If you're using python3.4 explicitly, you should be using pip3.4 specifically as well. Otherwise, just use python3 and pip3. For Python 2, you can simply use python (which, unless you installed the Homebrew version as well), will be the system Python), and ditto for pip. python2.7 and pip2.7 may also work.
In general, to find out which Python version goes with which pip you're using, try:
pip --version
and you'll see the Python included in the result.

No need to worried about if you have multiple version of Python and Pip installed. just check your version by writing in terminal :
$ brew info python
or to check the version of pip write in terminal :
$ brew info pip
and make sure you have updated your both pip and python version (write in terminal $ brew upgrade pip/python)
and other way to install python is go to https://www.python.org/downloads/ and choose as your requirement, there is two version available 2.7.9 & 3.4.3 ,
after installing python write in terminal $ python -V to check its version :) Hope it will help :)

Installing numpy for Python 2.7 while also having Python 3.4 installed?

I have both Python 2.7 and Python 3.4 (and have to have both because for the class I'm running, students have the option of using either). One student has used Python 2.7 and numpy for their project, but when I attempt to install numpy, it installs it to 3.4. I need to install it to 2.7.
I'm using numpy 1.9 from this site, which I'm told is also 2.7-specific: http://sourceforge.net/projects/numpy/files/NumPy/
However, nonetheless it still goes to the 3.4 folder. Copying it to Python 2.7 didn't work, obviously.
How do I do this?

I recommend installing with pip.
pip install numpy
If this doesn't work on windows then download the binary from http://www.lfd.uci.edu/~gohlke/pythonlibs/ and convert it to a wheel before installing.
pip install wheel
wheel convert path/to/binary
pip install numpy_wheel
Pip is recommended because you can uninstall.
To check where you are installing to
pip -V
You may have an environmental variable path to the wrong pip.

Assuming that you are using, or at least you should use pip to install the library. You can specify the python version to be installed by changing the suffix, e.g. pip-2.7 install numpy.
pip install numpy
pip-2.7 install numpy
pip-3.4 install numpy
As an alternative, in case that you do not want to use pip is to download and install the library using setup with a similar technique.
python setup.py install
python2.7 setup.py install
python3.4 setup.py install

Your PATH isn't setup correctly.
C:> where pip
Should tell you which pip it is trying to use, and it is likely whichever one it found on your PATH first...
So, instead, you will want to run it as
C:> C:\mypython2install\pip.exe install numpy
Or, setup your path correctly. See here

Just one other note on issues like this. I had a similar problem with Python 2.7 libraries not being found, because I had miniconda installed for a Python virtual environment that was hijacking calls to python from other programs. After deleting the minconda directory in my home the problem went away and python libraries that were properly installed were found again.

Note-This answer is particularly for Windows PC which has both Python2 & Pyhton3 installed on it.
Both the versions of Python has their different directories somewhat like
"C:\Python27\" ----for python2
"C:\Python35\" ---- for python3
*(or it depends on what path you chose while installing Python**)*
pip GENERALLY exist under the directory "C:\Python**\Scripts"
there you can find exe files like:
pip.exe/pip2.exe/pip2.7.exe ----for python2
pip3.exe/pip3.5.exe ----for python3
to install packages on python2:
use
Python27\Scripts\pip2.exe install package_name
(where the 1st argument is the path of exe file, it might differ for your system)
to install packages on python3:
use
Python35\Scripts\pip3.exe install package_name
there is no need to uninstall any version of python to achieve the task.

Python can't get requests installed on Ubuntu for Python 2.7

All I want to do is run a Python script that requires Python 2.7 & Requests on my Ubuntu 10.04 EC2 box.
I installed Python 2.7, no problem. "python" by itself still points to python 2.6, which is very annoying, b/c I'm not sure how ubuntu will freak if I change the symlink /usr/bin/python to point to 2.7.
I followed the (carefully buried) install instructions for pip (at http://www.pip-installer.org/en/latest/index.html, and which are WAY too hard to find if they aren't the ABSOLUTE FIRST command on the "install pip" page)
So, the real problem here is that pip install requests completes successfully, but only installs for python 2.6, not 2.7. The pip usage instructions say nothing about how to install a package for a specific version of python.
How do I do this?
I just want to run my python script that requires 2.7 + requests.

First install pip for your 2.7 distribution using easy_install (easy_install should definitely be included with your 2.7 distribution):
easy_install-2.7 -U pip
Then install what you need:
pip-2.7 install requests
Then you can run code with python2.7 instead of python.

Yeah it would be a bad idea to change the link pointing to which python version. Instead, can you change the shebang to say #!/usr/bin/env python2.7 instead of #!/usr/bin/env python ?

Though python2.7 /path/to/pip install requests might work; you should install pip for python2.7 separately instead.
If you don't use virtualenv then invoke pip as pip-2.7 (the command is available if you install pip for python2.7).
Follow installation instructions which is the first item in the table of contents. Substitute python with python2.7 in the instructions.