Frequently asked questions

Before skimming this list, please make sure you have the latest version of VIP. Please go and check the repository now. Alternatively, you can run:

pip install --upgrade vip_hci

On linux, why do I get a matplotlib related error when importing VIP?

ImportError: Matplotlib qt-based backends require an external PyQt4,
PyQt5, or PySide package to be installed, but it was not found.

You may need to change the matplotlib backend. Find your matplotlibrc configuration file and change the backend from WXAgg to TkAgg (or the appropriate backend for your system). More info here: On linux the matplotlibrc file is located in:


I get a RuntimeError (Python is not installed as a framework) in macOS when using python3 and conda.

This is caused by using matplotlib with virtual environments or conda in macOS, and has nothing to do with VIP. See Working with Matplotlib on OSX in the Matplotlib FAQ for more information.

The VIP script doesn’t finish the job, it seems to be stuck.

This is very unlikely to happen with the latest versions of pip, setuptools and VIP’s setup script. If you encounter this situation just kill the process (Ctrl + C) and start it again by re-running the setup command. A workaround is to install the problematic dependency before executing VIP setup:

$ pip install <problematic_dependency>

Why does the setup fail complaining about the lack of a Fortran compiler?

Fortran compilers are apparently needed for compiling scipy from source. Make sure there is a Fortran compiler in your system. A workaround is to install scipy through conda before running the setup script:

$ conda install scipy

Why do I get and error related to importing cv2 package when importing VIP?

cv2 is the name of Opencv bindings for python. This library is needed for fast image transformations, it was the default library before v1.0.0 (although it was optional). Starting from v1.1.0 the opencv library should be installed upon installation of VIP, although the default image library became ‘vip-fft’. For old VIP versions, you can install opencv manually with conda:

$ conda install opencv

Why do I get a warning related to DS9/XPA when importing VIP?

Please make sure you have DS9 and XPA in your system path. Try installing them using your system’s package management tool.

Why does Python crash when using some of the parallel functions, e.g. pca_annular and mcmc_negfc_sampling?

These functions require running SVD on several processes and this can be problematic depending on the linear algebra libraries on your machine. We’ve encountered this problem on OSX systems that use the ACCELERATE library for linear algebra calculations (default in every OSX system). For this library the multiprocessing is broken. A workaround is to compile Python against other linear algebra library (e.g. OPENBLAS). An quick-n-easy fix is to install the latest ANACONDA (2.5 or later) distribution which ships MKL library and effectively replaces ACCELERATE on OSX systems. On linux with the default LAPACK/BLAS libraries VIP successfully distributes the SVDs among all the existing cores. With conda you can run:

$ conda install mkl

I get an error: ValueError: “unknown locale: UTF-8” when importing VIP.

It’s not VIP’s fault. The problem must be solved if you add these lines in your ~/.bash_profile:

export LC_ALL=en_US.UTF-8
export LANG=en_US.UTF-8

Where is the specfit module?

From versions 1.0.0 to 1.0.3, specfit was a module of VIP offering atmosphere retrieval and spectral characterisation of directly imaged companions. Given the divergence with the original purpose of VIP, starting from version 1.1.0, it has been renamed, expanded, moved to a separate GitHub repository and converted into its own package (called special).