EMIR, the near-infrared camera and multi-object spectrograph operating in the spectral region from 0.9 to 2.5 microns, has been commissioned at the Nasmyth focus of the Gran Telescopio Canarias. One of the most outstanding capabilities of EMIR is its multi-object spectroscopic mode. This work describes how important reduction steps, concerning image rectification and wavelength calibration of spectroscopic data, are performed with the help of PyEmir, the Python code developed as part of the contribution of the Universidad Complutense de Madrid in this instrument.