This is the fourth post-O2 release of PyCBC for analysis of data taken during Advanced LIGO's second observing run and Advanced Virgo's first observing run. This release has been tested against LALSuite with the hash: 8cbd1b7187ce3ed9a825d6ed11cc432f3cfde9a5 This release fixes some issues with v1.9.0's optimal_snr code, adds in the ability to generate omega scans in workflows, and includes some minor bug-fixes and the usual ongoing development. Details of the changes since the last release are at https://github.com/ligo-cbc/pycbc/compare/v1.9.0...v1.9.1 A Docker container for this release is available from the pycbc/pycbc-el7 repository on Docker Hub and can be downloaded using the command: docker pull pycbc/pycbc-el7:v1.9.1 On a machine with CVMFS installed, a pre-built virtual environment is available for Red Hat 7 compatible operating systems by running the command: source /cvmfs/oasis.opensciencegrid.org/ligo/sw/pycbc/x86_64_rhel_7/virtualenv/pycbc-v1.9.1/bin/activate and for Debian 8 compatible operating systems by running the command: source /cvmfs/oasis.opensciencegrid.org/ligo/sw/pycbc/x86_64_deb_8/virtualenv/pycbc-v1.9.1/bin/activate A bundled pycbc_inspiral executable for use on the Open Science Grid is available at /cvmfs/oasis.opensciencegrid.org/ligo/sw/pycbc/x86_64_rhel_6/bundle/v1.9.1/pycbc_inspiral