The switching effect in thin films of poly(diphenylene phthalide), a non-conjugated and wide-band gap dielectric polymer of the poly(arylene phthalide) class, is investigated. However, at thicknesses below the critical submicron value, electronic switching to a state with high conductivity, initiated by various effects, is observed in the films. Switching can be caused by changing the electrical voltage, the thickness of the polymer film, and the mechanical uniaxial pressure. Switching caused by a change in the electronic parameters of the metal at the metal/polymer interface in particular is of great interest. It was found that phase transition, superconducting transition, and elastic and inelastic deformations lead to the switching of the polymer film. In this case, it is possible to initiate both switching to the "on" state and to the "off" state. A mechanism is proposed that explains this effect in terms of band-like conductivity. The transport of the polymer's charge carriers occurs along a narrow conductivity band located in the middle of the band gap. Studies using different methods confirmed the presence of groups of electronic states in the Fermi level of the polymer, as well as deep states. With a band gap width of 4.2 eV, the injection maximum is located near the middle of the band gap at a level of 2.4 eV.