# Build/Install FAQ

How do I set up a development version of SciPy in parallel to a released version that I use to do my job/research?

If you use the `conda` package manager, this is covered in the Development environment quickstart guide (macOS).

Another simple way to achieve this is to install the released version in site-packages, by using a binary installer or pip, for example, and set up the development version in a virtualenv. First, install virtualenv (optionally, use virtualenvwrapper), then create your virtualenv (named scipy-dev here) with:

    $ virtualenv scipy-dev

Now, whenever you want to switch to the virtual environment, you can use the command `source scipy-dev/bin/activate`, and `deactivate` to exit from the virtual environment and back to your previous shell. With scipy-dev activated, first install Scipy’s dependencies:

    $ pip install numpy pytest cython pybind11

After that, you can install a development version of Scipy, for example, via:

    $ python setup.py install

The installation goes to the virtual environment.

How do I set up an in-place build for development?

For development, you can set up an in-place build so that changes made to `.py` files have effect without rebuild. First, run:

    $ python setup.py build_ext -i

Then you need to point your PYTHONPATH environment variable to this directory. Some IDEs (Spyder, for example) have utilities to manage PYTHONPATH. On Linux and OSX, you can run the command:

    $ export PYTHONPATH=$PWD

and on Windows:

    $ set PYTHONPATH=/path/to/scipy

Now, editing a Python source file in SciPy allows you to immediately test and use your changes (in `.py` files), by simply restarting the interpreter.

If you use the macOS, please find more information in the Development environment quickstart guide (macOS).