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brew installs latest python3 but python3 not updated?

Hello I'm trying to upgrade my python from macos
I enter command 'brew upgrade python3' and it tells me the latest version is installed (Warning: python3 3.9.1_8 already installed)
but then when I type 'python3 -V' it returns 'Python 3.6.1'
and when I try to 'brew link --overwrite python#3.9' the operation proceeds successfully but there is still no change.
What am I missing? Why am I not able to use Python3.9?

Most likely the PATH variable in your environment is not configured correctly and the shell is finding the wrong python3.
You can check for the path to the current python3 command using:
which python3
Most likely the output will not be pointing at the brew installation that is usually:
/usr/local/bin/python3
If that was the case check the PATH variable in your environment using:
echo $PATH
or:
env | grep PATH
and check whether /usr/local/bin is present in the PATH variable and that it has precedence over the folder where your current python3 is located.
Change it by edited the .profile file in your home directory by adding:
export PATH="/usr/local/bin:$PATH"

I highly recommend that you install and use pyenv. It is somewhat standard way of managing multiple Python versions on your Mac. I have 4 different Python versions, and switch from one to the other with ease. It can do a lot more than just set your global Python version. Check it out: https://github.com/pyenv/pyenv. It can be installed with brew pyenv.

pip installs packages successfully, but executables not found from command line

I am working on mac OS X Yosemite, version 10.10.3.
I installed python2.7 and pip using macport as done in
http://johnlaudun.org/20150512-installing-and-setting-pip-with-macports/
I can successfully install packages and import them inside my python environment and python scripts. However any executable associated with a package that can be called from the command line in the terminal are not found.
Does anyone know what might be wrong? (More details below)
For example while installing a package called "rosdep" as instructed in http://wiki.ros.org/jade/Installation/Source
I can run: sudo pip install -U rosdep
which installs without errors and corresponding files are located in /opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages
However if I try to run : sudo rosdep init,
it gives an error : "sudo: rosdep: command not found"
This is not a package specific error. I get this for any package installed using pip on my computer. I even tried adding
/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages
to my $PATH.
But the executables are not found on the command line, even though the packages work perfectly from within python.

I know the question asks about macOS, but here is a solution for Linux users who arrive here via Google.
I was having the issue described in this question, having installed the pdfx package via pip.
When I ran it however, nothing...
pip list | grep pdfx
pdfx (1.3.0)
Yet:
which pdfx
pdfx not found
The problem on Linux is that pip install ... drops scripts into ~/.local/bin and this is not on the default Debian/Ubuntu $PATH.
Here's a GitHub issue going into more detail: https://github.com/pypa/pip/issues/3813
To fix, just add ~/.local/bin to your $PATH, for example by adding the following line to your .bashrc file:
export PATH="$HOME/.local/bin:$PATH"
After that, restart your shell and things should work as expected.

Solution
Based on other answers, for linux and mac you can run the following:
echo "export PATH=\"`python3 -m site --user-base`/bin:\$PATH\"" >> ~/.bashrc
source ~/.bashrc
instead of python3 you can use any other link to python version: python, python2.7, python3.6, python3.9, etc.
instead of .bashrc, choose the rc file from your favourite shell.
Explanation
In order to know where the user packages are installed in the current OS (win, mac, linux), we run:
python3 -m site --user-base
We know that the scripts go to the bin/ folder where the packages are installed.
So we concatenate the paths:
echo `python3 -m site --user-base`/bin
Then we export that to an environment variable.
export PATH=\"`python3 -m site --user-base`/bin:\$PATH\"
Finally, in order to avoid repeating the export command we add it to our .bashrc file and we run source to run the new changes, giving us the suggested solution mentioned at the beginning.

On macOS with the default python installation you need to add /Users/<you>/Library/Python/2.7/bin/ to your $PATH.
Add this to your .bash_profile:
export PATH="/Users/<you>/Library/Python/2.7/bin:$PATH"
That's where pip installs the executables.
Tip: For non-default python version which python to find the location of your python installation and replace that portion in the path above. (Thanks for the hint Sanket_Diwale)

check your $PATH
tox has a command line mode:
audrey:tests jluc$ pip list | grep tox
tox (2.3.1)
where is it?
(edit: the 2.7 stuff doesn't matter much here, sub in any 3.x and pip's behaving pretty much the same way)
audrey:tests jluc$ which tox
/opt/local/Library/Frameworks/Python.framework/Versions/2.7/bin/tox
and what's in my $PATH?
audrey:tests jluc$ echo $PATH
/opt/chefdk/bin:/opt/chefdk/embedded/bin:/opt/local/bin:..../opt/local/Library/Frameworks/Python.framework/Versions/2.7/bin...
Notice the /opt/local/Library/Frameworks/Python.framework/Versions/2.7/bin? That's what allows finding my pip-installed stuff
Now, to see where things are from Python, try doing this (substitute rosdep for tox).
$python
>>> import tox
>>> tox.__file__
that prints out:
'/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/tox/__init__.pyc'
Now, cd to the directory right above lib in the above. Do you see a bin directory? Do you see rosdep in that bin? If so try adding the bin to your $PATH.
audrey:2.7 jluc$ cd /opt/local/Library/Frameworks/Python.framework/Versions/2.7
audrey:2.7 jluc$ ls -1
output:
Headers
Python
Resources
bin
include
lib
man
share

If you're installing using --user (e.g. pip3.6 install --user tmuxp), it is possible to get the platform-specific user install directory from Python itself using the site module. For example, on macOS:
$ python2.7 -m site --user-base
/Users/alexp/Library/Python/2.7
By appending /bin to this, we now have the path where package executables will be installed. We can dynamically populate the PATH in your shell's rc file based on the output; I'm using bash, but with any luck this is portable:
# Add Python bin directories to path
python3.6 -m site &> /dev/null && PATH="$PATH:`python3.6 -m site --user-base`/bin"
python2.7 -m site &> /dev/null && PATH="$PATH:`python2.7 -m site --user-base`/bin"
I use the precise Python versions to reduce the chance of the executables just "disappearing" when Python upgrades a minor version, e.g. from 3.5 to 3.6. They'll disappear because, as can be seen above, the user installation path may include the Python version. So while python3 could point to 3.5 or 3.6, python3.6 will always point to 3.6. This needs to be kept in mind when installing further packages, e.g. use pip3.6 over pip3.
If you don't mind the idea of packages disappearing, you can use python2 and python3 instead:
# Add Python bin directories to path
# Note: When Python is upgraded, packages may need to be re-installed
# or Python versions managed.
python3 -m site &> /dev/null && PATH="$PATH:`python3 -m site --user-base`/bin"
python2 -m site &> /dev/null && PATH="$PATH:`python2 -m site --user-base`/bin"

The Installing Packages tutorial on python.org describes how to locate the binary directory:
On Windows
You can find the user base binary directory by running
python -m site --user-site and replacing site-packages with Scripts.
For example, this could return
C:\Users\Username\AppData\Roaming\Python36\site-packages so you
would need to set your PATH to include
C:\Users\Username\AppData\Roaming\Python36\Scripts.
On Linux and macOS
On Linux and macOS you can find the user base binary directory by
running python -m site --user-base and adding bin to the end. For
example, this will typically print ~/.local (with ~ expanded to the
absolute path to your home directory) so you’ll need to add
~/.local/bin to your PATH.

I stumbled upon this question because I created, successfully built and published a PyPI Package, but couldn't execute it after installation. The $PATHvariable was correctly set.
In my case the problem was that I hadn't set the entry_pointin the setup.py file:
entry_points = {'console_scripts':
['YOUR_CONSOLE_COMMAND=MODULE_NAME.FILE_NAME:FUNCTION_NAME'],},

On Windows, you need to add the path %USERPROFILE%\AppData\Roaming\Python\Scripts to your path.

Windows and Python 3.9 from MS Store
I have a different path with python -m site --user-base and python -m site - yes, the second command without --user-base to get all sites - as the other answers here state:
C:\Users\<your User>\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages
Why is my path different
Because I installed python from MS Store
Solution
Put the above path in your path and replace site-packages with scripts

When you install Python or Python3 using MacOS installer (downloaded from Python website) - it adds an exporter to your ~/.profile script. All you need to do is just source it. Restarting all the terminals should also do the trick.
WARNING - I believe it's better to just use pip3 with Python3 - for future benefits.
If you already have Python3 installed, the following steps work for me on macOS Mojave:
Install ansible first using sudo - sudo -H pip3 install ansible
you create a symlink to the Python's bin path
sudo ln -s /Library/Frameworks/Python.framework/Versions/Current/bin /Library/Frameworks/Python.framework/current_python_bin
and staple it to .profile
export PATH=$PATH:/Library/Frameworks/Python.framework/current_python_bin
run source ~/.profile and restart all terminal shells.
Type ansible --version

In addition to adding python's bin directory to $PATH variable, I also had to change the owner of that directory, to make it work. No idea why I wasn't the owner already.
chown -R ~/Library/Python/

I solve the problem!
Use pip3 instead pip.
pip3 install foobaz
vim ~/.zshrc and add:
export PATH="/Users/your_name/Library/Python/3.8/bin:$PATH"
source ~/.zshrc
Now MacOS has shifted the default terminal from bash to zsh. Therefore, you have to source zshrc but not bashrc or bash_profile.
foobaz -v

had the same issue with macOS Monterey. I had to modify my .bash_profile file and add the following entry
export PATH="~/Library/Python/3.8/bin:$PATH"
The default python version on macOS Monterey is 3.8, but you will have to double check your python version to make sure you're using the correct one

Python: aliased to python3

I tried to upgrade python 2.7 to python 3 and I modified the file ~/.bash_aliases but when I type python in elementary terminal I get this error
zsh: command not found: python3
and when I type which python
python: aliased to python3
actually I prefer return to python 2.7 or if someone know how can I fix this :c

Go into your .zshrc file. Is there a line that reads:
alias python='python3'
If so, remove that line. Else, check if you can run python2, python2.7, or something like that. If so, then just hack and add the line
alias python='python2'
Or whatever your python2 is. Else, type
sudo apt-get install python2.7
Or whatever is the appropriate method for installing programs on your system.

Follow this steps if you are using macOS.
Install Python with brew: brew install python. This will install the latest version of Python. If you want Python 2.7, do well to specify the version.
Check the path where this Python was installed: brew info python. You will see a path similar to: /usr/local/opt/python#3.9/libexec/bin
Make home brew Python default:
$ echo 'export PATH="/usr/local/opt/python#3.9/libexec/bin:$PATH"' >> ~/.zshrc
Source the file to apply changes without restarting the terminal: source ~/.zshrc

How do I use brew installed Python as the default Python?

I try to switch to Homebrew (after using fink and macport) on Mac OS X 10.6.2. I have installed python 2.7 with
brew install python
The problem is that, contrary to Macport, it seems that there is no python_select utility, and my default mac python is always default
which python
give me
/usr/bin/python
and /usr/bin/python is not a symlink
How can I do to make python brew flavour to be my default python ?

As suggested by the homebrew installer itself, be sure to add this to your .bashrc or .zshrc:
export PATH="/usr/local/opt/python/libexec/bin:$PATH"

As you are using Homebrew the following command gives a better picture:
brew doctor
Output:
==> /usr/bin occurs before /usr/local/bin This means that system-provided programs will be used instead of those provided by
Homebrew. This is an issue if you eg. brew installed Python.
Consider editing your .bash_profile to put: /usr/local/bin ahead of
/usr/bin in your $PATH.

See: How to symlink python in Homebrew?
$ brew link --overwrite python
Linking /usr/local/Cellar/python/2.7.3... 28 symlinks created
$ which python
/usr/local/bin/python

Quick fix:
Open /etc/paths
Change the order of the lines (highest priority on top)
In my case /etc/paths looks like:
/usr/local/bin
/usr/local/sbin
/usr/bin
/bin
/usr/sbin
/sbin
If you want to know more about paths in OSX I found this article quite useful:
http://muttsnutts.github.com/blog/2011/09/12/manage-path-on-mac-os-x-lion/

I did "brew install python" for OSX High Sierra. The $PATH had /usr/local/bin before any other path but still which python was pointing to the system's python.
When I looked deeper I found that there is no python executable at /usr/local/bin. The executable is named python2. To fix this problem create a symbolic link python pointing to python2:
/usr/local/bin $: ln -s python2 python

For Apple Silicon machines, the path are slightly different. After running brew install python, you must ensure your ~/.zshrc uses the correct Homebrew paths:
# Homebrew
eval "$(/opt/homebrew/bin/brew shellenv)"
# Homebrew: Python
export PATH="/opt/homebrew/opt/python/libexec/bin:$PATH"
Results:
% which python
/opt/homebrew/opt/python/libexec/bin/python
% python --version
Python 3.9.9
% which pip
/opt/homebrew/opt/python/libexec/bin/pip
% pip -V
pip 21.3.1 from /opt/homebrew/lib/python3.9/site-packages/pip (python 3.9)

python formula now uses python3(v3.6.5 for now), brew will link the directory:
/usr/local/opt/python -> ../Cellar/python/3.6.5
it will also link the binary:
/usr/local/bin/python3 -> ../Cellar/python/3.6.5/bin/python3
If you still need to use python2.x, use:
brew install python#2
To use homebrew's python, just put its directory in PATH, for bash:
export PATH="/usr/local/opt/python/libexec/bin:$PATH"
for fish:
set -x PATH /usr/local/opt/python/libexec/bin $PATH
Note:
doing this will shadow the system default version of python
homebrew used to link python to /usr/local/share/python in older versions.

Homebrew does NOT replace stuff in "/usr/bin". You'll just want to put "/usr/local/bin" ahead of "/usr/bin" in your path, then "which python" will give you "/usr/local/bin/python".
Replacing /usr/bin/python (or /usr/bin/ruby) is highly unrecommended.

Modify your $PATH, Add this in your bashrc or bash_profile:
export PATH=/usr/local/bin:/usr/local/sbin:~/bin:$PATH
more click here:
Issue #89791

I did brew install python, my $PATH was good, but still, which python gave me the system installed one. Restarting the terminal fixed it.

You need to edit your PATH environmental variable to make sure wherever the homebrew python is located is searched before /usr/bin. You could also set things up in your shell config to have a variable like PYTHON be set to your desired version of python and call $PYTHON rather than python from the command line.
Also, as another poster stated (and especially on mac) DO NOT mess with the python in /usr/bin to point it to another python install. You're just asking for trouble if you do.

python now points to python3, if you need python 2 then do:
brew install python#2 and then in your .zshrc or .bashrc file
export PATH="/usr/local/opt/python#2/libexec/bin:$PATH"
Now, pyhon --version = Python 2.7.14 and python3 --version = Python 3.6.4.
That's the behavior I'm used to seeing in my terminal.

I believe there are means to make homebrew python default, but in my opinion the proper way to solve a problem is not to mess with system python paths: it is better to create a virtualenv in which homebrew python would be default (by using virtualenv --python option). Using tools like python_select is almost always a bad idea.

Use pyenv instead to install and switch between versions of Python. I've been using rbenv for years which does the same thing, but for Ruby. Before that it was hell managing versions.
Consult pyenv's github page for installation instructions. Basically it goes like this:
- Install pyenv using homebrew. brew install pyenv
- Add a function to the end of your shell startup script so pyenv can do it's magic. echo -e 'if command -v pyenv 1>/dev/null 2>&1; then\n eval "$(pyenv init -)"\nfi' >> ~/.bash_profile
Use pyenv to install however many different versions of Python you need. pyenv install 3.7.7.
Set the default (global) version to a modern version you just installed. pyenv global 3.7.7.
If you work on a project that needs to use a different version of python, look into pyevn local. This creates a file in your project's folder that specifies the python version. Pyenv will look override the global python version with the version in that file.

Add the /usr/local/opt/python/libexec/bin explicitly to your .bash_profile:
export PATH="/usr/local/opt/python/libexec/bin:$PATH"
After that, it should work correctly.

Just do:
brew install python
brew link python
After doing that, add this to your bashrc or bash_profile:
alias python='/usr/local/bin/python2'
Enjoy!

You can edit /etc/paths. Here is mine:
/usr/local/bin
/usr/bin
/bin
/usr/sbin
/sbin
Then add a symlink for the python version. In my case
$ cd /usr/local/bin
$ ln -s python3 python
Voila!

If you are fish shell
echo 'set -g fish_user_paths "/usr/local/opt/python/libexec/bin" $fish_user_paths' >> ~/.config/fish/config.fish

try this
which python3
Try typing python3 instead of just python

Greeting folks! I have the need to use python 3.10 version to harness its new features. My solved solution at 2022-07-03 is as follows. Have fun coding python!
» rm '/usr/local/bin/pip3.10'
» brew link python#3.10
» echo 'export PATH="/usr/local/opt/python#3.10/bin:$PATH"' >> ~/.zshrc
» python3
Python 3.10.5 (main, Jun 23 2022, 17:15:25) [Clang 13.1.6 (clang-1316.0.21.2.5)] on darwin
Type "help", "copyright", "credits" or "license" for more information.

Since High Sierra, you need to use:
sudo chown -R $(whoami) $(brew --prefix)/*
This is because /usr/local can no longer be chowned

brew link python
And you must create/add an alias for python and put it in your .zprofile (Located in Users/username folder, if you press Shift+command+.
This must point to your homebrew python installation location.
alias python ='opt/homebrew/bin/python3'

No idea what you mean with default Python. I consider it bad practice to replace the system Python interpreter with a different version. System functionality may depend in some way on the system Python and specific modules or a specific Python version. Instead install your custom Python installations in a safe different place and adjust your $PATH as needed in order to call you Python through a path lookup instead of looking for the default Python.

switch versions of python

Story:
One of the app that i have works on python 2.4 and other on 2.6. I tried to do a sym link of python2.4 to python and things started to break loose on ubuntu jaunty.
Now i am downloading every dependency of 2.4 and installing it using python2.4 setup.py install. The dependencies seem to be endless.
Question1: How will i tell any framework that go and use version so and so pf python like day django to use 2.6 and say mjango to use 2.4? Something like we say use database databasename kinda syntax.
Question2: Is there more elegant way to switch between version as my hack of symlinking was a virtual disaster?
Question3: Can I download a deb for say hardy and make jaunty believe its for her?

Use Virtualenv.
There is more information here: Working with virtualenv.
Using virtualenv you can create a new virtual python environment with whatever version of Python you want for each project or application. You can then activate the appropriate environment when you need it.
To expand on my answer:
You can install multiple versions of Python on your computer (I have 2.4, 2.5, 2.6 and 3.1 on my machine - I install each from source). I use a Mac, and keep my system Python as whatever OS X sets as the default.
I use easy_install to install packages. On ubuntu you can get easy_install like this:
sudo apt-get install python-setuptools
To install virtualenv then do:
easy_install virtualenv
I tend to create a new virtualenv for each project I'm working on and don't give it access to the global site-packages. This keeps all the packages tight together and allows me to have the specific versions of everything I need.
virtualenv -p python2.6 --no-site-packages ~/env/NEW_DJANGO_PROJECT
And then whenever I am doing anything related to this project I activate it:
source ~/env/NEW_DJANGO_PROJECT/bin/activate
If I run python now it uses this new python. If I use easy_install it installs things into my new virtual environment.
So, virtualenv should be able to solve all of your problems.

Pythonbrew is a magical tool. Which can also be called as Python version manager similar to that of RVM-Ruby version manager but Pythonbrew is inspired by Perlbrew.
Pythonbrew is a program to automate the building and installation of Python in the users $HOME.
Dependencies – curl
Before Installing the Pythonbrew, Install “curl” in the machine, to install curl use the below command in the terminal, give the the password for the user when prompted.
$sudo apt-get install curl
After Installing the curl, Now Install Pythonbrew, copy and paste the following commands in the terminal and type the password for the user when prompted.
Recomended method of installation - Easy Install
$ sudo easy_install pythonbrew
To complete the installation, type the following command
$pythonbrew_install
Alternate method of installation:
Use curl command to download the latest version of pythonbrew from github.
curl -kLO http://github.com/utahta/pythonbrew/raw/master/pythonbrew-install
After downloading, change “pythonbrew-install” to “executable”
chmod +x pythonbrew-install
Then, run the pythonbrew-install in the terminal
./pythonbrew-install
Now the Pythonbrew has been installed in the “Home Directory” i.e., /home/user/.pythonbrew
Next, copy and paste the following line to the end of ~/.bashrc
*NOTE: change “user” to your user name in the system
source /home/user/.pythonbrew/etc/bashrc
Thats it! Close the terminal.
Steps to Install different versions of Python:
Open a new terminal, type the following command or copy and paste it.
$pythonbrew install 2.6.6
This will install Python 2.6.6 and to install Python 2.7 or Python 3.2, change the version number in the previous command.
$pythonbrew install 2.7
or
$pythonbrew install 3.2
Update: If you get error while Installing then Install using the below command.
$pythonbrew install --force 2.7
or
$pythonbrew install --force 3.2
How to manage different versions of Python installed in system
For instance, if Python 2.6.6, Python 2.7 and Python 3.2 is installed in your system, switching between the versions can be done as follows:
By default, Python 2.6.6 will be active and in order to switch to Python 2.7 use the below command
$pythonbrew switch 2.7
The default Python is changed to Python 2.7.
Now, to switch to Python 3.2 change the version number in the previous command.
$pythonbrew switch 3.2
Use the below command to check or list the installed Python versions
$pythonbrew list
Use the below command to check or list the available Python Versions to install
$pythonbrew list -k
To uninstall any of the installed Python version (for example to uninstall Python 2.7), use the below command.
$pythonbrew uninstall 2.7
Use the below command to update the Pythonbrew
$pythonbrew update
Use the below command to disable the Pythonbrew and to activate the default version
$pythonbrew off
Enjoy the experience of installing multiple versions of Python in single Linux / ubuntu machine!

I find http://github.com/utahta/pythonbrew much easier to install and use than any other solution.
Just install it and you'll have these options:
pythonbrew install 2.7.2
pythonbrew use 2.7.2 # use 2.7.2 for a current terminal session
pythonbrew switch 2.7.2 # use 2.7.2 by default system wide
pythonbrew uninstall 2.7.2
Note: if you're using a Linux-based operating system with preinstalled Python, switching (system wide) to another version can make things go wrong, so be careful.

A more grassroot approach than Virtualenv is the side-by-side installation of two Python versions.
If there is an existing installation, and you want a second installation into the same root path (e.g. /usr/local), use this target when making install:
make altinstall
When your second installation is Python 2.6, this will leave you with a /usr/local/bin/python2.6 alongside the old /usr/local/bin/python.
A simple way to switch between these two versions is using a shell alias (alias python=/usr/local/bin/python2.6) on the shell where you invoke the interpreter. But this won't work across sub-shells and she-bang invocations.

pyenv is yet another Python manager. The README.md at that link has a good set of instructions, but they basically are:
$ cd
$ git clone git://github.com/yyuu/pyenv.git .pyenv
Then set up your $PATH.
$ echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.bash_profile
$ echo 'export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.bash_profile
$ echo 'eval "$(pyenv init -)"' >> ~/.bash_profile
Install the desired versions of Python:
$ pyenv install 2.7.8
After installing you need to run this:
$ pyenv rehash
Then switch to the version of Python you want to run, for the shell:
$ pyenv shell 2.7.8

"Question1: How will i tell any framework that go and use version so and so pf python like day django to use 2.6 and say mjango to use 2.4?"
You simply run them with the specific python version they need. Run mjango with /usr/bin/python2.4 and django with /usr/bin/python2.6. As easy as that.
"Question2: Is there more elegant way to switch between version as my hack of symlinking was a virtual disaster?"
Yes, see above. Have two separate installs of Python, and run explicitly with the different versions.
"Question3: Can I download a deb for say hardy and make jaunty believe its for her?"
That generally works. If it doesn't, it's because it has dependencies that exist in Hardy, and does not exist in Jaunty, and then you can't.
And here is a Question 4 you didn't ask, but should have. ;)
"Is there an easier way to download all those Python modules?"
Yes, there is. Install setuptools, and use easy_install. It will not help you with library dependecies for those Python modules that have C code and need to be compiled. But it will help with all others. easy_install will download and install all the Python dependencies of the module in question in one go. That makes it a lot quicker to install Python modules.

Move to the project directory :
Create an environment :
virtualenv -p python2.7 --no-site-packages ~/env/twoseven
Then activate your source :
source ~/env/twoseven/bin/activate