link between python and the windows command prompt

[yadin]

hi! i need to know how i can run ussal commands that i ussally type at
the windows command prompt from a python file. that is  for example
from the windows command prompt i ussually type "cd D:\folder\ nec2++ -
i inputfile.nec -o outputfile.out "  now how can i execute this
command that i ussually type at the windows command prompt from a
python file?
i know it has to do with the sys and os module but how specifically?
what commands? any references?