An electronic conducting polymer is submitted to strong structural variations during the doping (or dedoping) process due essentially to inclusion (or exclusion, respectively) of anions in its structure. The insertion (or exclusion) of ions induces a swelling (or deflation) phase and therefore modifications of the surface morphology. In this article we study these two correlated phenomena, surface morphological variations and swelling process, by scanning tunneling microscopy (STM) of a polypyrrole film as a function of its doping state. In order to account best for the modifications induced by the electrode potential, the STM images are obtained in situ. This allows us to follow the evolution of the swelling process and the surface morphological variations associated with the electrodoping mechanism.