def introduction():
    'Prints out introductory statements at start of run.'
    print('Lennard-Jones potential')
    print('Cut-and-shifted version for dynamics')
    print('Cut (but not shifted) version also calculated')
    print('Diameter, sigma = 1')
    print('Well depth, epsilon = 1')
    if fast:
        print('Fast NumPy force routine')
    else:
        print('Slow Python force routine')
Prints out introductory statements at start of run.
def introduction():
    
    print('Lennard-Jones potential')
    print('Cut-and-shifted version for dynamics')
    print('Cut (but not shifted) version also calculated')
    print('Diameter, sigma = 1')
    print('Well depth, epsilon = 1')
    if fast:
        print('Fast NumPy force routine')
    else:
        print('Slow Python force routine')