The work of an expanding gas

You will compare the work a gas does in one step and reversibly.

The idea. Against a constant outside pressure, $w = -p_\text{ex}\Delta V$, and $1$ L bar $= 100$ J. Reversibly at constant temperature, $w = -nRT\ln\dfrac{V_f}{V_i}$, which is the same as $-2.303\,nRT\log\dfrac{V_f}{V_i}$.

Your tasks.

1. In work_constant, return the work in J for a pressure in bar and volumes in L.
2. In work_reversible, return the reversible isothermal work in J.
3. In how_many_times, the gas expands from v1 to v2. Find how many times more work it does reversibly than in one step against its final pressure.