Parity violating asymmetry in inclusive π0 or π+ meson production by longitudinally polarized electrons on unpolarized protons, is calculated as a function of the momentum transfer square k2 and the total energy W of the πN system. We consider the ∆ contribution in the s channel, the standard Born contributions and the vector mesons (ρ and ω) exchanges in the t channel. The parity-odd term is the sum of two contributions. The main term (found to be linear in k2) comes from the isovector component of the electromagnetic currents. It is model independent and can be calculated exactly in terms of fundamental constants. The second term is isoscalar in nature. Near threshold and in the ∆ region, it is found to be much smaller (in absolute value) than the isovector one.