pip fails to find brew installed libs with M1 chip - python

folks, with new M1 chip brew stores its libraries in the different location /opt/homebrew/ instead of /usr/local/.
And now when pip needs some packages installed by brew(in my case leveldb for plyvel)it's not able to find it until I use Rosetta brew version to put in the old directory: /usr/local/.
I've added eval "$(/opt/homebrew/bin/brew shellenv)" in my .zshrc to import brew-related vars and I thought it should do the thing but no lack.
Do you have any tips on how to handle this issue?

I don't know whether there is a Right Way to do this, but one was is to pass the necessary compiler flags as an environment variable:
CFLAGS="-I/opt/homebrew/include -L/opt/homebrew/lib" python3 -m pip install plyvel

The correct solution to this problem is to include homebrew path in LDFLAGS
export LDFLAGS=-L/opt/homebrew/lib/
and then run the pip command. It is best to add this to your bash / zsh profile (~/.bashrc or ~/.zshrc).

Related

How to install a Python package inside a virtual environment with Pip (OS X)

Edit:
I'm going to close this question as the reason its happening is different from my original assumption, and it's clearer to ask the question anew:
Pip installs packages in the wrong directory with virtualenv
The accepted answer doesn't directly answer the original question, but is a very useful overview.
Based on discussion below the issue is that even after
$ source ~/PycharmProjects/Practice/venv/bin/activate
$ pip install numpy
numpy is installed in /usr/local/lib/python2.7/site-packages
What could the reason for this be?
Original:
Using Python on OS X via Homebrew:
I've been trying much of the day to sort this out but either I get a must supply either home or prefix/exec-prefix -- not both error, or the package I try to install goes into totally the wrong place:
$ pip3 --version
pip 18.1 from /usr/local/lib/python3.7/site-packages/pip (python 3.7)
$ cd venv
$ pip3 install numpy
..... [snip with following error:]
"must supply either home or prefix/exec-prefix -- not both")
Using this hint
$ pip3 install numpy -t .
Then I get a new error,
`Command "python setup.py egg_info" failed with error code 1 in /private/var/folders/.../pip-install-0fvveq3v/package/'
Searching around SO gives various possibilities involving pip install setuptools. but pip install throws the above error or installs in the wrong place. i.e. the solution involves something that's causing the error in the first place.
I tried to use the Python.org installer but it didn't install pip at all. (The custom installer showed the option checked but with size zero).
An introductory overview is available in this nice tutorial. Here is a good summary with more detail. But, if you renamed or moved the virtual env dir after its creation, it could break it. Create a new one from scratch: $ cd ~/PycharmProjects; python3 -mvenv newenv ; Activate: $ source newenv/bin/activate ; Install something: $ pip install colorama (same as pip3 install only if venv activated); Check: ls ~/PycharmProjects/newenv/lib/python3*/site-packages ; Deactivate: $ deactivate
Then you could try this solution for Pycharm: how to associate a virtual environment with a python project in pycharm. PyCharm indeed comes bundled with virtualenv which could have been customized, please look into Pycharm-specific resources: creating virtual environments and installing packages in Pycharm.
If you have installed PyPI's mainstream virtualenv, by default it will create new environments with the python interpreter that virtualenv was installed with. But it's possible to specify an alternate Python Interpreter upon a new env creation: $ virtualenv -p python3.7 newenvname
Regarding the error DistutilsOptionError: must supply either home or prefix - please check this and this for solutions. Homebrew'ed mappings between python and pip are described here. The normal pip install --user is disabled in homebrewed Python, but there are workarounds. MacOS system Python doesn't provide pip, but it can installed, reinstalled or upgraded for any specific python version manually. Original non-brewed installers are also available for all Python versions: https://www.python.org/downloads/mac-osx/
By default there's no pip.conf, but it can be created by hand to customize things. All possible pip.conf locations (per-user, per-venv, and global/system-wide, and how they override each other) are listed here. If someone faces an issue, they could use pip config list command to see their active configuration, or locate pip.conf and find it.
Finally, you may want to ensure you aren't using pip against macOS' system python. Shell commands such as $ brew info python, which pip, which pip3, pip3 -V, which python3 can help you see what you actually use. Since the macOS default $PATH used to be /usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin, stock macOS binaries (including python) may take precedence over some homebrew'ed installations (including python). If so, a custom PATH could be exported via the ~/.bashrc if required.

Use default Python while having Anaconda

For development in Python, I am using Miniconda on my Mac with macos Sierra. However, I have to use a framework that only works with the default Python (present at /usr/bin/python).
My question is: How can I install packages for this default Python? If I use pip some-package, this will automatically install the package for the root conda environment.
EDIT: As discussed in the comments, I agree it is a bad idea to mess with the system default version of Python. Instead, I would like this SDK to work in a conda environment or with Python 2.7 installed from python.org. However, none of these seem to work! How to get this working?
You are not trying to install any package, you are trying to install very specific package pynaoqi that require external SDK, that is compiled for the specific architecture. You should edit your question to reflect that.
According to what I saw on the Net, it is not a trivial task. First, make sure you have the version 2.5 of the SDK, that suits the MacOS version. Then, look at this script. As they say, in order to work the dynamic libraries should be renamed.
By the way, you need 64-bit Python 2.7.
To install packages using the system Python you can use /usr/bin/easy_install, which ships with MacOS.
You may wish to install pip from there, by running:
sudo easy_install pip
Once you have pip installed, you won't be able to use it directly if the conda pip command is shadowing it. You have multiple options here, depending on your tastes. You may choose to alias the system pip to alias systempip=/usr/bin/pip, or have /usr/bin in front of /Users/user/anaconda/ in your $PATH.
As mentioned in other answers, messing with the system Python is not recommended, things may break, and you can (most) certainly get any package to work within a conda environment.
Some packages don't work out of the box with Anaconda's Python for some people because the distribution would default to a non-framework build of Python. A common complaint came from users of matplotlib, for example, who could not get figure windows to display properly. Fortunately, conda offers a framework build of python as well, named pythonw or pythonw3. Maybe you can try to get your package to work with pythonw, if that is where your problems come from.
Try this, find your way to path/to/python/scripts:
/usr/bin/python/scripts
And run pip here.
pip some-package is installing for the root anaconda environment because it is using pip from anaconda library. Anaconda add anaconda root dir to path before /usr/bin/ . so when you use pip if finds it on anaconda root. check path of pip using which pip, this will tell you complete path of pip.
You can install it on default python using /usr/bin/python -m pip install some-package. or use /path/to/default/pip install some-package.
The common issue is that anaconda (or miniconda) will have a python executable and pip executable in its bin directory.
If you truly need to run /usr/bin/python, this leads to the annoying conclusion: you cannot put conda in your path.
This lead me to some annoying machinations in my .bash_profile. You can use the same techniques for you, but your exact path to conda may differ:
# variables for using Conda
export BASE_PATH=$PATH
export CONDA_PATH="/Users/cmerriam/l/miniconda2/bin"
export CONDA_BIN="$CONDA_PATH/conda"
export CONDA_ACTIVATE="source $CONDA_PATH/activate"
export CONDA_DEACTIVATE="source $CONDA_PATH/deactivate"
# prompt function for [conda: myenv] when it is on.
function conda_branch {
type $CONDA_BIN >/dev/null 2>&1 && $CONDA_BIN info --envs | grep \* | awk '{print $1;}' | grep -v '^root'
}
function conda_part {
echo "[conda:$(conda_branch)]" | grep -v "\[conda:\]"
}
# Conda alias set
alias c="echo \"
cls = list conda environments
con <name> = activate conda environment
coff = deactivate conda environment
conda create -n tensorflow python=3.6 anaconda tensorflow jupyter
conda remove --name tensorflow --all
echo \\\$CONDA_DEFAULT_ENV\""
alias cls="$CONDA_BIN info --envs"
alias con="$CONDA_ACTIVATE"
alias coff="$CONDA_DEACTIVATE"
Option 2:
You may find you just need to run the same version or PYTHONPATH as /usr/bin/python. Then you make a conda environment with that version:
conda create -n myenv python=2.7
or, set a PYTHONPATH
export PYTHONPATH=/usr/lib/python2.7/site-packages
Option 3:
Uninstall Conda. It is a good tool for a set of problems that is not your current set of problems.
I too have a Mac with Sierra.
Assumption: Let's say you have Anaconda. Now you would have DefaultPython(python2) and say this Anaconda is of Python3.
Secret: The way any shell/default python selected is with PATH variable set in a shell. So when you install Anaconda, installer shall try to set new path variables to your default bash shell
Solution: Have one python (2 or 3) as default. For the less used one, try using full path. If you have to use
Cheat code: create /usr/bin/python as symbolic link to the python's actual repo(save the old one). This can be altered according to your usage.
Hope this works!
I am not sure I correctly understood your problem, but if the problem is that you want to easily switch between several versions of python like system python, other versions of python, different versions of miniconda or anaconda bound to specific versions of python (that is not just virtual environments) on your mac, then the best solution is pyenv.
It automatically relinks where your current /usr/bin/python, /usr/bin/pip and other binaries like ipython currently look at depending on the context. There are several options of what context is, but I usually use system python as default and pyenv local for each project which basically puts a file with the version name in your current directory and each time you cd in the directory or its subdirecories /usr/bin/python is automatically switched to that version you selected.
You need to manage your PATH environment variable. I like to keep functions in my shell profile to turn conda "on" and "off." So, on a Mac for example:
deactconda() {
export PATH="${PATH/\/Users\/<your_usrname>\/anaconda\/bin:/}"
}
actconda() {
export PATH=$HOME/anaconda/bin:$PATH
}
Then, whenever you want to stop using conda, just type deactconda at the prompt, etc.
You can do this multiple ways, first by providing the path to the pip in your default location,
your_default_python_path/pip install package
for example if you have a python 2.7 then,
sudo /usr/local/bin/pip2.7 install networkx
This should do the trick for you. After that you can install any packages and invoke them using default python(mine is 2.7 here)
with pip version 0.8 onwards you can also specify sudo /usr/local/bin/pip-2.x install package as well

pip is configured with locations that require TLS/SSL, however the ssl module in Python is not available

I am using Python 3.6. When I try to install "modules" using pip3, I face this issue:
pip is configured with locations that require TLS/SSL, however the ssl module in Python is not available
For Windows 10
if you want use pip in normal cmd, not only in Anaconda prompt. you need add 3 environment paths.
like the followings:
D:\Anaconda3
D:\Anaconda3\Scripts
D:\Anaconda3\Library\bin
most people only add D:\Anaconda3\Scripts
MAC OS
I had the same problem on Mac OS(Mojave) and solved the problem as mentioned on this link - Openssl issue.
If you do not have Homebrew or don't know what is Homebrew:
/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
Or if you already have Homebrew installed:
brew update && brew upgrade
brew uninstall --ignore-dependencies openssl; brew install https://github.com/tebelorg/Tump/releases/download/v1.0.0/openssl.rb
Update:
Keep in mind, that I had to use --ignore-dependencies flag, because other packages installed that depend on OpenSSL.
Additional if the problem is caused after using pyenv, you can fix it by using:
brew reinstall python
For Debian users, the following may be of use:
sudo apt install libssl-dev libncurses5-dev libsqlite3-dev libreadline-dev libtk8.6 libgdm-dev libdb4o-cil-dev libpcap-dev
Then cd to the folder with the Python 3.X library source code and run:
./configure
make
make install
I'm using Windows 10 and installed Miniconda 3 with Python 3.7.
I solved this error by following this https://github.com/conda/conda/issues/8273
Specifically, I copied the following files from C:\Users\MyUser\Miniconda3\Library\bin to C:\Users\MyUser\Miniconda3\DLLs:
libcrypto-1_1-x64.dll
libcrypto-1_1-x64.pdb
libssl-1_1-x64.dll
libssl-1_1-x64.pdb
For centos 7:
Install openssl:
sudo yum install openssl-devel
now goto python directory were we extracted the python tar,
run below commands
sudo ./configure
sudo make
sudo make install
This will fix the problem in centos...
For future Oracle Linux users trying to solve this, below is what worked for me.
First install missing libs:
yum install zlib-devel bzip2-devel openssl-devel ncurses-devel sqlite-devel
readline-devel tk-devel gdbm-devel db4-devel libpcap-devel xz-devel
Then cd to your Python3.X library and run:
make
make install
macOS, pyenv
In case of your python being an pyenv installed one, where pyenv is installed with homebrew on macOS, there might me a newer version available which fixes this:
$ brew update && brew upgrade pyenv
Then reinstalling the python version:
$ pyenv install 3.7.2
pyenv: /Users/luckydonald/.pyenv/versions/3.7.2 already exists
continue with installation? (y/N)
Note, it is a bit dirty to overwrite the existing python install like that, but in my case it did work out. Probably cleaner to delete it and then recreate it properly.
For Windows 10,windows 7
If pip install is not working on CMD prompt, run it using Anaconda prompt - it works.
https://github.com/pypa/virtualenv/issues/1139
Worked for me.
sudo apt-get install libssl-dev
Use this to enable ssl for pip.
Let me know if someone encounters issues.
Encountered this issue while installing python 3.8 from source on ubuntu. The steps needed to install it successfully alongside the default python 3.7 are summarised below :
sudo apt -y install libssl-dev zlib1g-dev build-essential
wget https://www.python.org/ftp/python/3.8.0/Python-3.8.0.tgz
tar -xf Python-3.8.0.tgz
cd Python-3.8.0/
./configure --enable-optimizations
make
sudo make altinstall
The install instruction for zlib1g-dev and build-essential is redundant, as ubuntu desktop already has these, but was necessary for some of Amazon's EC2 instances. python 3.8.0 is the current release just now, but should be replaced with the latest available.
These instructions are best for keeping python 3.7 as the default for python3, and running python 3.8 in a virtual environment.
Similar to the above solution reinstall the python version with pyenv.
Somehow, I upgraded my openssl which broke the pyenv version python.
pyenv install 3.6.8
python-build: use openssl#1.1 from homebrew
python-build: use readline from homebrew
...
The first line says it relies on the homebrew openssl.
In my case, I reinstalled Python. It solved the problem.
brew reinstall python
For OpenSUSE in the same manner, but a few changes of listed above packages:
zypper install zlib-devel libopenssl-devel ncurses-devel sqlite3-devel readline-devel tk-devel gdbm-devel libpcap-devel xz-devel
Then cd to Python sources dir and
make
make install
or
make
make altinstall
And perhaps
ln -s /usr/local/lib64/python3.6/lib-dynload/ /usr/local/lib/python3.6/lib-dynload
should be executed for OpenSUSE users. See Python 3.7 install not working on openSUSE Leap 42.3
Just try installing through Anaconda prompt
I ran into this issue with Visual Studio Code installing pylint from the VS Code prompt.
I was able to overcome the issue by opening the Anaconda installation directory and running
pip install pylint
Then VS Code was happy, but that did not fix the issue as running
& C:/Users/happy/Anaconda3/python.exe -m pip install -U pylint
pretty much gave the same error so it seems that VS Code is unable to access the python modules.
Note that VS Code picks up the first python env it see when installed, the bottom left of the screen indicates which env is being used. Clicking on that area allows to set the environment. So even if you ran the pip install for an environment VS Code could be looking at a different one.
Best approach was to make sure that VS code had the correct python environment selected and that same environment is in the system PATH (under System Properties --> Advanced --> Environmental Variables)
Under the Path Variable, Edit and browse to the specific Anaconda directory that you want VSCode to use and add to PATH, I needed to Add the following:
C:\Users\happy\Anaconda3\
C:\Users\happy\Anaconda3\Scripts\
C:\Users\happy\Anaconda3\Library\bin\
C:\Users\happy\Anaconda3\Library\mingw-w64\bin\
Your Anaconda installation directory may differ.
One note is that Windows does not have the PATH variable take effect until you restart the terminal. In this case close and re-op VS code. If using a Terminal or PS Shell then close and reopen and check Path to make sure it is included.
The problem probably comes from your installed openssl package version. That was the case for me and I fixed this issue just upgrading it. I'm on Mac OS, using brew :
brew upgrade openssl
If you installed python with brew, this should directly fix the issue with it, as python is dependent on openssl
Newest Python 3.8.4 or higher should able to support https protocol out of box. If you still have old python installation on your pc - either download & install python3 manually, or using Chocolatey:
If you don't have Chocolatey, install it - from here: https://chocolatey.org/docs/installation
You can just copy paste one command line liner and execute it from command prompt with elevated priviledges.
choco install python3
if you don't have python3 installed, or you you have it installed - then:
choco upgrade python3
Notice also that you can use also anaconda distribution, as it has built-in python with https support, but this rather ancient instructions, no need to follow them anymore.
Install anaconda, using command line:
choco install anaconda3
Set environment variables:
set PATH=C:\tools\Anaconda3\Scripts;C:\tools\Anaconda3;C:\tools\Anaconda3\Library\bin;%PATH%
and then run command which failed. In my case it was:
pip install conan
Anaconda uses separate python installation, and pip is also anaconda specific.
As Tokci said, it also works for Windows 7.
"Go with the mouse to the Windows Icon (lower left) and start typing "Anaconda". There should show up some matching entries. Select "Anaconda Prompt". A new command window, named "Anaconda Prompt" will open."
Then pip works.
The following also helped to import xgboost:
https://www.youtube.com/watch?v=05djBSOs1FA
If someone is using Arch Linux OS, I solved the TLS/SSL problem by running this:
sudo pacman -S openssl
Then I could use pip to install the package I needed:
pip install openpyxl
Go to Anaconda prompt and type (if you have python 3.x installed on your engine) :
py -m pip install pymysql
i was having the same issue and this solved my problem. later after doing this you can import pymysql in power shell or any other prompt.
The issue is due to OpenSSL package is missing on your PC.
If pip install openpyxl also gives error.
you can fix this by installing OpenSSL(Win64 OpenSSL v1.1.1g) from below site :
slproweb.com/products/Win32OpenSSL.html
Restart the IDE you are using, for changes to be in effect.
In Windows 10 SQL Server 19 the solution is known.
Copy the following files:
libssl-1_1-x64.dll
libcrypto-1_1-x64.dll
from the folder
C:\Program Files\Microsoft SQL Server\MSSSQL15.MSSQLSERVER\PYTHON_SERVICES\Library\bin
to the folder
C:\Program Files\Microsoft SQL Server\MSSSQL15.MSSQLSERVER\PYTHON_SERVICES\DLLs
Then open a new DOS command shell prompt.
From https://learn.microsoft.com/en-us/sql/machine-learning/troubleshooting/known-issues-for-sql-server-machine-learning-services?view=sql-server-ver15#7-unable-to-install-python-packages-using-pip-after-installing-sql-server-2019-on-windows
Worked for me.
pkg install openssl
Use this to enable ssl.
Currently there is same issue in Anaconda prompt (Anaconda3) on Windows 10. Here is workaround: https://github.com/ContinuumIO/anaconda-issues/issues/10576
Fixed this without having to change anything related to TSL/SSL.
I was trying to see if the same thing was happening to pip, and saw that pip was broken. Did some digging and realized it's probably caused by Homebrew deleted python#2 on February 1st, 2020.
Running brew uninstall python#2 to delete python2 installed by Homebrew.
Destroyed the virtual env created using python3 and created a new one. pip3 installing works fine again.
I am on macOS and I had used brew but what Vaulstein mentioned in his answer didn't cover my case.
I run the following commands to make sure my current python was not installed by brew
brew list | grep python
python
python#2
brew info python
python#3.8: stable 3.8.3 (bottled)
Interpreted, interactive, object-oriented programming language
https://www.python.org/
Not installed
...
So I download the latest 3.8.5 from https://www.python.org/ and when installing it I saw following information
Certificate verification and OpenSSL
This package includes its own private copy of OpenSSL 1.1.1. The
trust certificates in system and user keychains managed by the
Keychain Access application and the security command line utility are not used as defaults by the Python ssl module
After installed 3.8.5 it fixed the problem.
I got into this problem using Ubuntu, pyenv and Python 3.8.1 managed by pyenv. There was actually no way to get pip to work correctly, since every time I tried to install anything, including pip itself, the same error showed up.
Final solution was to install, via pyenv, a newer version, in this case 3.8.6. Apparently, from 3.8.4 Python is prepared to run SSL/TLS out of the box, so everything worked fine.
I simply solved the problem with following command:
brew upgrade python#3.9
SSL is included by default on this version!
In my case I was running into issues with my $PATH on Linux. This can also happen on MacOS.
Check to see if /usr/bin/pip3 install package_name_goes_here works for you. If so then run
which pip3 this will tell you which is the first directory that pip3 is installed in.
If it is something like /usr/local/bin/pip3 which is different from /usr/bin/pip3 then you may need to adjust your $PATH.
Run
echo $PATH and copy the result.
The PATH is simply a colon separated list of directories that contain directories. Bash will always return the first instance of the program that you are attempting to execute. Move all the system directories upfront. Here is a list of some of the system directories:
/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin
If that fails then verify you have openssl installed by running openssl version -a if not then install openssl.
If you've installed anaconda via scoop, and encounter this error while using pip from within a conda environment you can resolve it by...
Adding these to your path
C:\Users\YOUR_USERNAME\scoop\apps\anaconda3\current
C:\Users\YOUR_USERNAME\scoop\apps\anaconda3\current\Scripts
C:\Users\YOUR_USERNAME\scoop\apps\anaconda3\current\Library
C:\Users\YOUR_USERNAME\scoop\apps\anaconda3\current\Library\bin
Installing openssl via scoop
scoop install openssl
And copying the following DLLs from ..\anaconda3\Library\bin to ..\anaconda3\DLLs
References:
https://stackoverflow.com/a/54897379
https://stackoverflow.com/a/60405693

Python not finding pip modules MacOS

I have installed some modules using pip and whenever I try to import them in Python I am told that no module exists. I think there is something wrong with my paths. This is some terminal output, does anyone know how I can fix this?
Nicks-MacBook-Pro:~ nickporter$ which python
/usr/bin/python
Nicks-MacBook-Pro:~ nickporter$ which pip
/usr/local/bin/pip
Nicks-MacBook-Pro:~ nickporter$
You can use pip freeze to find the packages installed.
I do not know whether you use a virtualenv. If you use it, you have to source it, to activate it.
It looks like you probably have multiple installations of Python or pip (or both). First, determine if you have multiple Python binaries installed and decide on the one you want to use by default.
You clearly have /usr/bin/python...check if there is another one in /usr/local/bin/python. If you do have one in /usr/local/bin, I'm guessing you installed it with Homebrew. Pick the Python you want to use (if there are multiple) by playing with your PATH. If you want to use /usr/local/bin/python (assuming it exists) ensure /usr/local/bin comes before /usr/bin in your PATH.
Once you do that, I would remove your current pip. After you remove it, look for it again with which pip, just to make sure you don't have any old one laying around. Once you've totally removed it, reinstall.
If you're installing with Homebrew, I'd stick to using the Homebrew python and pip. If you're not using Homebrew I'd install pip using: https://bootstrap.pypa.io/get-pip.py
curl -q https://bootstrap.pypa.io/get-pip.py | sudo python
You have homebrew version of python shadowed by the system python, but because system python doesn't have pip, a pip you see is actually a brew one.
I found, that the reason for this is that brew by default names python2.7 as python2 in /usr/local/bin (probably for preventing possible compatibility issues with some system services (?)) , i.e. you may try to run python2 or try to ln /usr/local/bin/python2 /usr/local/bin/python and restart the term session.
Make sure that /usr/local/bin goes before /usr/bin and /bin in your $PATH.
BTW. brew info {package} often contains recommendations for proper configuration of packages.

Brew fails to install Python: can not symlink

I'm trying to install python 2.7 on the latest version of OSX using brew but I get the following error...
.app bundles were installed.
Run `brew linkapps` to symlink these to /Applications.
Warning: Could not link python. Unlinking...
Error: The `brew link` step did not complete successfully
The formula built, but is not symlinked into /usr/local
You can try again using `brew link python'
Possible conflicting files are:
/usr/local/bin/pip
/usr/local/bin/easy_install-2.7
/usr/local/bin/easy_install
Would anyone know how to fix this error? I tried brew link python but this did not work. I'm new to Linux/OSX, so if this is really obvious, I would still appreciate it if someone could point me in the right direction!
The error means those files already exist in /usr/local/bin
If you 'ls -lF' on that dir, are they sym links that point to a path with the word 'cellar' in it?
If so, then brew already put them in place for you. You're probably missing /usr/local/bin from your PATH
If not, then something else put them there earlier. On a fresh mac, that directory is empty. Brew is a better way to manage those files, so if it was my machine I would remove those files from /usr/local/bin, then you can run brew link. I'd probably keep them in another spot temporarily in case I later discovered a need for them.
Also, run brew doctor when you have a chance. It will tell you about any other problems like this.
Brew wants to own /usr/local/bin. I would let it, it's a great tool.
Fix for macOS Mojave 10.14.2 (2018-12)
I was able to install python with brew using these commands.
brew install python
sudo chown -R $(whoami) $(brew --prefix)/*
sudo install -d -o $(whoami) -g admin /usr/local/Frameworks
brew link python
python3 --version
The most likely answer is that you have somehow installed executables (notably pip and easy-install) that Homebrew packages with it's install of Python outside of the Homebrew workflow. Because Homebrew is not managing these executables (that is, the executables are not symlinks to the versions stored in Homebrew's Cellar repository), its default action is to not overwrite these executables. There are two options you have to resolve this:
You can remove the files that are blocking the installation. Depending on how you installed the executables previously, you might have to do this through manual rm commands. Once you do that, you can run brew link python and Homebrew will happily form the symlinks now that there are no pre-existing executables.
You can tell Homebrew you don't actually care that those executables exist, and you want to overwrite them anyways by using brew link --overwrite python as described in this answer.
In either case, be aware that both pip and easy-install will have dependency files in a site-packages folder somewhere on your computer from their original installation. It would be advisable for you to audit your Python install and your computer for extraneous site-packages folders.

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