Virtual Environments¶
Getting Started¶
Creating a virtualenv¶
We’ll be using virtualenv so our installation experiments are contained and don’t modify your system Python environment. If you aren’t already familiar with virtualenv, you may want to read up on it first.
Create a virtualenv:
$ virtualenv --no-site-packages pip_test_env
We use the --no-site-packages
flag to prevent this virtualenv from
“seeing” your global Python “site-packages” directory, so that our
experiments aren’t confused by any Python packages you happen to
already have installed globally.
Recent versions of virtualenv (1.4+) automatically install pip for you
inside the virtualenv (there will already be a pip
script in
pip_test_env/bin/
). If you are using a pre-1.4 virtualenv, run
pip_test_env/bin/easy_install pip
to install pip in the virtual
environment.
Note
If you are using Windows, executable scripts in the virtualenv will
be located at pip_test_env\Scripts\
rather than
pip_test_env/bin/
. Just replace all occurrences of the latter
with the former.
Let’s “activate” the virtualenv to put pip_test_env/bin
on our
default PATH, so we can just type pip
instead of
pip_test_env/bin/pip
:
$ . pip_test_env/bin/activate
Note
The leading dot is important. Without it, a subshell is spawned and only that subshell gets the virtualenv activated. The leading dot tells the shell to run the activate script in the current shell.
On Windows, this is:
$ pip_test_env\Scripts\activate.bat
In either case, your shell prompt should now begin with
(pip_test_env)
to remind you that a virtualenv is activated. When
you are done working with this virtualenv type deactivate
to
remove its bin directory from your PATH.