Question for a script!!

I use an hydro tool developped by the Mineasota Gov.

Description: This script creates a raster whose cells measure the length of time
in seconds, that it takes water to flow across it and then accumulates
the time from the cell to the outlet of the watershed. water velocity
is calculated as a function of hydraulic radius, Manning's N and slope
Using a DEM as a source, flow direction, flow accumulation and slope (percent)
is calculated.

This tool creates a lot of raster by on various imputs and formulas.
I would like to change a formula:, this is the original:
exp = '(' + str(hydRad1) + ' * (' + flowAcc + ' * ' + cellSqMilesStr + ')) + ' + str(hydRad2) + ''

What I would like is : hydRad1 * ((' + flowAcc + ' * ' + cellSqMilesStr + ') ^ hydRad)

Thank you!