import yt

# Load the dataset.
ds = yt.load("IsolatedGalaxy/galaxy0030/galaxy0030")

# Create a slice plot for the dataset.  With no additional arguments,
# the width will be the size of the domain and the center will be the
# center of the simulation box
slc = yt.SlicePlot(ds, "z", ("gas", "density"))

# Create a list of a couple of widths and units.
# (N.B. Mpc (megaparsec) != mpc (milliparsec)
widths = [(1, "Mpc"), (15, "kpc")]

# Loop through the list of widths and units.
for width, unit in widths:

    # Set the width.
    slc.set_width(width, unit)

    # Write out the image with a unique name.
    slc.save("%s_%010d_%s" % (ds, width, unit))

zoomFactors = [2, 4, 5]

# recreate the original slice
slc = yt.SlicePlot(ds, "z", ("gas", "density"))

for zoomFactor in zoomFactors:

    # zoom in
    slc.zoom(zoomFactor)

    # Write out the image with a unique name.
    slc.save("%s_%i" % (ds, zoomFactor))