Calculating molarity, weight concentration from absorbance value for plasmonic nanoparticles in solution

It is common to measure the peak absorbance of the plasmonic nanoparticles in solution and then get the following:

1. Molarity (moles/liter)
2. Number of particles per ml
3. Weight concentration (ug/ml)

I wrote a small python function to extract these parameters.  The following inputs are needed for the function

1. d_nm :   diameter of the particle in nanoparticle
2. od :  peak OD measured from the absorbance plot
3. path_length_cm :  cuvette length in centimeter
4. density_g_per_cm3 :  for gold it is 19.28, for silver it is 10.49
5. molar_Extinction_perM_percm :  Molar extinction coefficient extracted from here.
6. This can extracted from measuring absorbance at different concentrations and then fitting a linear line. the slope will be molar extinction coefficient

Here is the code.