  The half lives are calculated for the process of $\beta^\pm$ decay and
electron capture for nuclei in mass range $\sim$ 65 - 100 relevant for the core
of a massive star at late burning stage of steller evolution that leads to
supernova explosion. The rates of electron capture process are also computed
for nuclei relevant during presupernova stage of massive stars. These half
lives and rates are calculated by expressing $\beta^\pm$ Gamow-Teller decay
strengths in terms of smoothed bivariate strength densities. These strength
densities are constructed in the framework of spectral averaging theory for two
body nuclear Hamiltonian in a large nuclear shell model space. The method has a
natural extension to weak interaction rates for r and rp-processes.
