function to compute the distance deltaR between two objects given their eta and phi coordinates

deltaR.py

def deltaR(eta1, eta2, phi1, phi2):
    import math
    '''
    Definition:
    -----------
        Function that calculates DR between two objects given their etas and phis
    Args:
    -----
        eta1 = float, eta of first object
        eta2 = float, eta of second object
        phi1 = float, phi of first object
        phi2 = float, phi of second object
    Output:
    -------
        deltaR = float, distance between the two objects 
    '''
    DEta = abs(eta1-eta2)
    DPhi = math.acos(math.cos( abs( phi1-phi2 ) ) ) # hack to avoid |phi1-phi2| larger than 180 degrees
    return math.sqrt( pow(DEta,2) + pow(DPhi,2) )