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Use UCSF Chimera Python API in a standard Python 2.7 interpreter.

Project Description

Use UCSF Chimera packages in any Python 2.7 interpreter

With PyChimera you can…

  • Run scripts depending on chimera from CLI with pychimera.
  • Enable import chimera in interactive coding sessions (console, ipython) outside Chimera.
  • Use Jupyter Notebooks with Chimera. You only need to run the prepopulated cell.
  • Launch a standard Chimera instance, with the benefit of importing all your conda or virtualenv packages with pychimera --gui.

I hope it’s useful! Feedback is appreciated!

While we intend to offer multiplatform support, it has been only tested on Linux. Some rough edges could arise in Windows & Mac. Please submit an issue if you find any problems!


First, if you haven’t already, install latest UCSF Chimera. We recommend using it inside a Python 2.7 conda environment.

Then, install PyChimera via pip or

pip install pychimera

git clone && python pychimera/ install


Run pychimera -h for quick help.

To start an interactive Python session:

pychimera                  # standalone
pychimera -i  # with some file
pychimera -im module       # with a Python module
pychimera -ic "string"     # with a command
pychimera ipython          # launch IPython interpreter
pychimera notebook         # launch IPython notebook

To launch a module that uses Chimera internally:

pychimera -m this

To execute any Python statement:

pychimera -c 'import chimera'

To execute a script:


To launch Chimera GUI with custom packages:

pychimera --gui

For developers

PyChimera provides access to Chimera’s modules from any Python 2.x interpreter. This is achieved in two steps:

  1. patch_environ() patches environment variables with proper paths (packages and libraries). Since the original sys.path is exported to PYTHONPATH, you can use all your virtualenv/conda packages with Chimera. This call restarts Python to inject a new os.environ with os.execve.
  2. enable_chimera() initializes Chimera. This is done through their own routines (chimeraInit).

PyChimera also offers its interface through python -m. This has not been tested, so it may not work. Add -i for interactive mode:

python -[i]m pychimera [-m another_module | -c "string" | | ipython | notebook]

You can also try to launch it from IPython, but, again, some things may not work. Anyway, these two commands have the same effect:

pychimera ipython [notebook]
ipython -m pychimera [notebook]

If you want to run a script with IPython and then inspect the results (-i flag), your best bet is to run pychimera ipython and then call %run path/to/ inside the interpreter.


Obviously, you need to install latest UCSF Chimera in your computer. PyChimera will do its best to find the installation path automagically in the standard locations. If somehow it doesn’t succeed, you can always set an environment variable called CHIMERADIR in your .bashrc, or similar.

export CHIMERADIR="~/.local/UCSF-Chimera"

Known issues

Chimera bundles its own distribution of some popular packages, like numpy, and those are loaded before your env packages for compatibility reasons. Be warned if you use specific versions for your project, because you can face strange bugs if you don’t take this into account.

In some platforms (Linux), this can be worked around with some work on the precendence of paths in sys.path, but in some of them not (OS X). The easiest and most robust way to fix this is by upgrading Chimera’s numpy:

pip install --upgrade numpy -t `pychimera --path`/lib/python2.7/site-packages

If you use the development version of pychimera, Chimera’s setuptools will complain about the versioning scheme (ie, pychimera==0.1.11+6.gc2e1fbb.dirty). As before, the fix is to upgrade the package. You might have to remove it beforehand, though:

rm -r `pychimera --path`/lib/python2.7/site-packages/setuptools-3.1*
pip install --upgrade setuptools -t `pychimera --path`/lib/python2.7/site-packages


Largely based on ideas by Greg Couch at chimera-users.


PyChimera is scientific software, funded by public research grants (Spanish MINECO’s project CTQ2014-54071-P, Generalitat de Catalunya’s project 2014SGR989 and research grant 2015FI_B00768, COST Action CM1306). If you make use of PyChimera in scientific publications, please cite it. It will help measure the impact of our research and future funding!

  author       = {Jaime Rodríguez-Guerra Pedregal and
                  Jean-Didier Maréchal},
  title        = {insilichem/pychimera: PyChimera},
  month        = apr,
  year         = 2017,
  doi          = {10.5281/zenodo.546883},
  url          = {}

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