  The properties of vortices in superconducting thin films are revisited. The
interaction between two Pearl vortices in an infinite film is approximated at
all distances by a simple expression. The interaction of a vortex with a
regular lattice of real or image vortices is given. The two spring constants
are calculated that one vortex in the vortex lattice feels when the surrounding
vortices are rigidly pinned or are free. The modification of these London
results by the finite size of real films is obtained. In finite films, the
interaction force between two vortices is not a central force but depends on
both vortex positions, not only on their distance. At the film edges the
interaction energy is zero and the interaction force is peaked. Even far from
the edges the vortex interaction considerably deviates from the Pearl result
and is always smaller than it.
