I’ve been wary of Anaconda but recently I’ve employed it to manage an environment shared between my OS X development machine and bonjovi, our Coop Lab server. Overall, I think it’s good technology as it greatly helps in minimizing time spent on installing software — which gets annoying as a scientist. Below are some of my notes on how to build up a project’s environment up from scratch.

## General Tips

Here are some general things to keep in mind – these are things I learned the hard way.

1. Don’t install Anaconda on OS X for all users – permissions will be wacky and cause issues.

2. Don’t use conda env export -n your-env to create environment.yml files for creating environments for a project across different operating systems. Conda may install OS-specific dependencies, which hinders portability. Instead handcraft a minimal environment YAML file with only top-level project dependencies (more on this below). Then, only use conda env export -n your-env > project_depends.yml for saving the versions of all dependencies for reproducibility reasons, not to reconstruct your environment on a different machine (thanks Joshua Shapiro and Jaime Ashander for this advice).

## Channels

Channels are like Homebrew’s kegs. You can add a new channel with:

$conda config --add channels r$ conda config --add channels bioconda
$conda config --add channels conda-forge These are the essential channels as far as I know. ## Building an environment interactively Each project needs its own environment (or a general environment, e.g. one for all projects requiring scipy, iPython, numpy, and R). Below I quick cover how I build up an environment. ### Create a new environment First, let’s create an example new environment, with only Python 3 and R: $ conda create -n rpy-base python=3.6.2 r=3.4.1

Now, we see this new environment:

$conda env list # conda environments: # default-fwdpy11 /Users/vinceb/anaconda/envs/default-fwdpy11 rpy-base /Users/vinceb/anaconda/envs/rpy-base root * /Users/vinceb/anaconda The asterisk indicates we’re currently using the root environment. This means all programs executed will use your default $PATH that looks in the usual places (.e.g /usr/local/bin).

Now, we switch to our new environment:

$source activate rpy-base (rpy-base) Note the $PATH now:

$echo$PATH
/Users/vinceb/anaconda/envs/rpy-base/bin:/usr/local/bin [...]
(rpy-base)

Our anaconda environment is now first in our search $PATH. ### Adding Packages To add new packages to a specific environment (e.g. not the root environment), we use: $ conda install install -n rpy-base r-tidyverse

This will ask you to proceed. After installation is complete, we see this R package (and its dependencies) are now in the environment:

$conda list # packages in environment at /Users/vinceb/anaconda/envs/rpy-base: # [...] r-tidyverse 1.1.1 r3.4.1_0 r ### Saving the Conda environment Now, we can export the environment to a YAML file which can be used to mirror the environment elsewhere. However, this is not recommended for maintaining project environments. The reason is that conda env export returns all packages and their dependencies installed, some of which may be OS X-specific and not portable to Linux servers. A better approach is to maintain a minimal list of packages used by your project, and let Conda find the appropriate dependencies on whatever machine it’s being run on. Then, the following can be used to make a manifest of the versions per system (for reproducibility, not for mirroring an environment): $ conda env export -n rpy-base > project_depends.yml

Ideally, then hand edit project_depends.yml to include only the minimal dependencies. We’ll call this rpy-base.yml — here is a minimal version example:

name: rpy-base
channels:
- conda-forge
- bioconda
- r
- defaults
dependencies:
- python=3.6.2=0
- r=3.4.1=r3.4.1_0
- r-tidyverse=1.1.1=r3.4.1_0

This clones a new repo:

$conda env create -n rpy-base2 -f rpy-base.yml which we see with: $ conda env list
# conda environments:
#
default-fwdpy11          /Users/vinceb/anaconda/envs/default-fwdpy11
rpy-base              *  /Users/vinceb/anaconda/envs/rpy-base
rpy-base2                /Users/vinceb/anaconda/envs/rpy-base2
root                     /Users/vinceb/anaconda

which we can now use source activate rpy-base2 to use.

### Removing an environment

Here’s how to delete an environment, such as the cloned environment rpy-base2 we just created.

$conda env remove rpy-base2 and now it’s gone: $ conda env list
# conda environments:
#
default-fwdpy11          /Users/vinceb/anaconda/envs/default-fwdpy11
rpy-base              *  /Users/vinceb/anaconda/envs/rpy-base
root                     /Users/vinceb/anaconda

### Python notebook hacks

Here’s an simple example script I use to start a Jupyter notebook kernel on a server that can be accessed locally through SSH forwarding.

#!/bin/bash

SERVER=bonjovi  # yes, bonjovi is the name of my server

if [[ "$1" == "client" ]]; then echo "setting up ssh forwarding..." ssh -N -f -L localhost:8888:localhost:8890$SERVER || (echo "error: ssh forwarding failed." && exit 1)
exit
fi

if [[ $# -lt 2 ]]; then echo "usage: bash launch_notebook.sh notebook.ipynb [server]" exit 1 fi source activate default-fwdpy11 if [[ "$2" == "server" ]]; then
jupyter notebook "$1" --no-browser --port=8890 else jupyter notebook "$1"
fi