What is 3f in Python

## @package python.DM_iterate
## @brief unkown python script prefix = autobuild.swdvlp64.opals.distro.demo
# example script showing how to load an OPALS datamanager
# and iterate through all points
# (script works in python 2 and 3)
from __future__ import print_function # print function syntax as in python 3
from opals.tools.flags import Debug_Mode
from opals import pyDM # for pyDM in release mode
from opals import pyDM_d as pyDM # for pyDM in debug mode
odm = "fullwave.odm" # odm test file
# load the "fullwave" data set from the opals demo distro
# pyDM.Datamanager.load parameter: filename (string), readOnly (bool) threadSafety (bool)
dm = pyDM.Datamanager.load (odm, True, False)
print ("Unable to open ODM '" + odm + "'")
# output some pyDM statistics
print ("ODM contains", dm.sizePoint (), "points")
print ("2D-limit (% .3f,"% limit.xmin, "% .3f) -"% limit.ymin, "(% .3f,"% limit.xmax, "% .3f)"% limit. ymax)
# create an attribute layout for iteration (optional)
lf = pyDM.AddInfoLayoutFactory ()
lf.addColumn (pyDM.ColumnSemantic.Amplitude)
lf.addColumn (pyDM.ColumnSemantic.EchoWidth)
print ("Output the first", maxOutput, "points of '" + odm + "'")
if sys.version_info> = (3, 0):
input ("Press Enter to continue ...")
raw_input ("Press Enter to continue ...")
# list the first points of the pyDM
for pt in dm.points (layout):
print ("Point", "% 5d"% i, "% .3f"% pt.x, "% .3f"% pt.y, "% .3f"% pt.z, "amp =% 4.0f" % pt.info (). get (0),
"ew =% 4.1f"% pt.info (). get (1))
print (i, "points listed")