  Here is the Python code based on the given instructions:
```
from dream import *

# Set the electric field strength
E_field = 1e6

# Set the electron density
n_e = 1e20

# Set the temperature
T_e = 1e6

# Define the momentum grid
momentum_grid = _generateMomentumGrid(n_e, T_e, E_field)

# Set up initial hot electron Maxwellian
hot_electron_distribution = RunawayElectronDistribution(n_e, T_e, E_field)

# Include Dreicer and avalanche in the equation system
include(Dreicer, Avalanche)

# Set up the radial grid and disable the runaway grid
radial_grid = RadialGrid(n_e, T_e, E_field)
radial_grid.disable_runaway_grid()

# Set the Svensson transport coefficients and use the nonlinear solver
set_transport_coefficients(Svensson)
set_solver(NonlinearSolver)

# Set the time stepper and save the settings to an HDF5 file
time_stepper = TimeStepper(momentum_grid, hot_electron_distribution, radial_grid)
time_stepper.save_settings_to_hdf5("settings.h5")
```