Instantaneous Amplitude, Phase and Frequency

Here is a link to a good discussion on this with MATLAB code.

Here is another place with a good discussion on doing a phase shift.
The Hilbert transform is fft ---> phase shift ---> ifft.
Doing fft and ifft are easy in numpy, and a phase shift is just multiplying each term in the signal by exp(j*p), where j is the imaginary unit, and p is the desired phase shift.