Installing scientific packages¶
Scientific software tends to have more complex dependencies than most, and it will often have multiple build options to take advantage of different kinds of hardware, or to interoperate with different pieces of external software.
In particular, NumPy, which provides the basis for most of the software in the scientific Python stack can be configured to interoperate with different FORTRAN libraries, and can take advantage of different levels of vectorised instructions available in modern CPUs.
Starting with version 1.10.4 of NumPy and version 1.0.0 of SciPy, pre-built
32-bit and 64-bit binaries in the
wheel format are available for all major
operating systems (Windows, macOS, and Linux) on PyPI. Note, however, that on
Windows, NumPy binaries are linked against the ATLAS BLAS/LAPACK library, restricted to SSE2
instructions, so they may not provide optimal linear algebra performance.
There are a number of alternative options for obtaining scientific Python libraries (or any other Python libraries that require a compilation environment to install from source and don’t provide pre-built wheel files on PyPI).
Building from source¶
The same complexity which makes it difficult to distribute NumPy (and many of the projects that depend on it) as wheel files also make them difficult to build from source yourself. However, for intrepid folks that are willing to spend the time wrangling compilers and linkers for both C and FORTRAN, building from source is always an option.
Linux distribution packages¶
For Linux users, the system package manager will often have pre-compiled versions of various pieces of scientific software, including NumPy and other parts of the scientific Python stack.
If using versions which may be several months old is acceptable, then this is likely to be a good option (just make sure to allow access to distributions installed into the system Python when using virtual environments).
Many Python projects that don’t (or can’t) currently publish wheel files at least publish Windows installers, either on PyPI or on their project download page. Using these installers allows users to avoid the need to set up a suitable environment to build extensions locally.
The extensions provided in these installers are typically compatible with the CPython Windows installers published on python.org.
As with Linux system packages, the Windows installers will only install into a system Python installation - they do not support installation in virtual environments. Allowing access to distributions installed into the system Python when using virtual environments is a common approach to working around this limitation.
The Wheel project also provides a wheel convert subcommand that can convert a Windows bdist_wininst installer to a wheel.
macOS installers and package managers¶
Similar to the situation on Windows, many projects (including NumPy) publish macOS installers that are compatible with the macOS CPython binaries published on python.org.
macOS users also have access to Linux distribution style package managers
Homebrew. The SciPy site has more details on using Homebrew to
install SciPy on macOS.
The SciPy site lists several distributions that provide the full SciPy stack to end users in an easy to use and update format.
Some of these distributions may not be compatible with the standard
virtualenv based toolchain.
Spack is a flexible package manager
designed to support multiple versions, configurations, platforms, and compilers.
It was built to support the needs of large supercomputing centers and scientific
application teams, who must often build software many different ways.
Spack is not limited to Python; it can install packages for
R, and other languages. It is non-destructive; installing
a new version of one package does not break existing installations, so many
configurations can coexist on the same system.
Spack offers a simple but powerful syntax that allows users to specify versions and configuration options concisely. Package files are written in pure Python, and they are templated so that it is easy to swap compilers, dependency implementations (like MPI), versions, and build options with a single package file. Spack also generates module files so that packages can be loaded and unloaded from the user’s environment.
The conda cross-platform package manager¶
Anaconda is a Python distribution published by Anaconda, Inc. It is a stable collection of Open Source packages for big data and scientific use. As of the 5.0 release of Anaconda, about 200 packages are installed by default, and a total of 400-500 can be installed and updated from the Anaconda repository.
conda is an open source (BSD licensed) package management system and
environment management system included in Anaconda that allows users to install
multiple versions of binary software packages and their dependencies, and
easily switch between them. It is a cross-platform tool working on Windows,
macOS, and Linux. Conda can be used to package up and distribute all kinds of
packages, it is not limited to just Python packages. It has full support for
native virtual environments. Conda makes environments first-class citizens,
making it easy to create independent environments even for C libraries. It is
written in Python, but is Python-agnostic. Conda manages Python itself as a
package, so that conda update python is possible, in contrast to
pip, which only manages Python packages. Conda is available in Anaconda and
Miniconda (an easy-to-install download with just Python and conda).