gmpy2 is an optimized, C-coded Python extension module that supports fast multiple-precision arithmetic. gmpy2 is based on the original gmpy module. gmpy2 adds support for correctly rounded multiple-precision real arithmetic (using the MPFR library) and complex arithmetic (using the MPC library). The gmpy2 2.0.x series is a stable version that is only receiving bug fixes. The main development branch (2.1.x) was extensively refactored. The most significant changes are support for thread-safe contexts and context methods. gmpy2 is available at https://pypi.python.org/pypi/gmpy2/ Documentation is available at https://gmpy2.readthedocs.io/en/latest/