(larch-installation)=
To install larch without building from source yourself, you'll need to use the conda package manager. If you already have conda installed, you can use that, otherwise you can download and install a free version.
Once you have conda installed, you can install Larch from the conda-forge
repository in a new environment called arboretum like this:
conda create -n arboretum -c conda-forge larchTo install larch without building from source yourself, you'll need to use the conda package manager. If you already have conda installed, you can use that, otherwise you can download and install a free version.
You should usually install conda for the local user, which does not require administrator permissions. You can also install conda system wide, which does require administrator permissions -- but even if you have those permissions, you may find that installing only for one user prevents problems arising over multiple users editing common packages.
If you already have Python installed, either by itself or as a companion to any one of a variety of common transportation planning tools (e.g., ArcGIS), you can still install and use conda. You do not need to uninstall, move, or change any existing Python installation. Just use the standard conda installer and let the installer add the conda installation of Python to your PATH environment variable. There is no need to set the PYTHONPATH environment variable.
Once conda is installed, on Windows it can be accessed from a preconfigured prompt (called "Anaconda Prompt", "Miniforge Prompt", or something similar) that will be installed in the Start menu. On linux and macOS, just use the regular terminal.
When you use conda to install Python, by default a base environment is
created and packages are installed in that environment. However, in general you should
almost never undertake project work in the base environment, especially if your
project involves installing any custom Python packages. Instead,
you should create a new environment for each project, and install the
necessary packages and dependencies in that environment. This will help
prevent software conflicts, and ensure that tools installed for one project
will not break another project.
The instructions below provide only the most basic steps to
set up and use an environment. Much more extensive documentation
on [managing environments](https://docs.conda.io/projects/conda/en/latest/user-guide/tasks/manage-environments.html)
is available in the conda documentation
itself.
If you'd like one command to just install Larch and a suite of related tools relevant for transportation planning and discrete choice analysis, you can create a new environment for Larch with one line.
conda env create jpn/taigaIf you've already installed the taiga environment and want to update it to the latest version, you can use:
conda env update jpn/taiga --pruneThe prune option here will remove packages that are not ordinarily included in the taiga environment; omit that function if you've installed extra packages that you want to keep.
When using the terminal (MacOS/Linux) or a conda prompt (Windows), the current environment name will be shown as part of the prompt:
(base) Computer:~ cfinley$By default, when opening a new terminal the environment is set as the
base environment, although this is typically not where you want to
be if you have followed the advice above. Instead, to switch environments
use the conda activate command. For example, to activate the taiga
environment installed in the quick start, run:
(base) Computer:~ cfinley$ conda activate taiga
(taiga) Computer:~ cfinley$The most convenient interface for interactive use of Larch is within JupyterLab. If it's not already installed in your base or working environments, you can install it using conda:
conda install -c conda-forge jupyterlabThen to start JupyterLab,
jupyter labJupyterLab will open automatically in your browser.