Q: How should I approach (in Python) to detect the change points in following time-series signal? I want to extract different signals present in this image. To do so, I want to find the boundaries of change point at 2.429 GHz, 2.444 GHz, and so on. Note: These numbers are observed visually and might change after statistical calculation.


A: The ruptures, changepoint or changefinder Python packages may do what you are looking for.  There is a tutorial on ruptures and changefinder here and the changepoint package here.
As the tutorial notes, another option is to call the R packages directly from Python using rpy2.
Depending on what you are measuring you will need to think about the type of changepoint you are seeking to identify.  Has the axis been truncated or are values lower than -110 not possible?  Typical packages assume Normal distribution with a change in mean and/or variance but others allow for changes in other distributions, trend, autocorrelation etc..
