Real-time quantitative PCR (qPCR) machines are well-suited for fluorescence measurements of molecular programming systems: they can precisely and programmably control the temper- ature of many samples while taking multiple-color, real-time fluorescence readings. However, their software is often narrowly focused on qPCR and other specific uses. Qslib is a Python library that adapts the Applied Biosystems QuantStudio 5 qPCR machine for more flexible and convenient use as a general-purpose programmable temperature control and fluorescence measurement device. As a Python library rather than a GUI, qslib is designed both to al- low everyday use through Jupyter notebooks, and to be readily extended for more complex applications