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if your varibles are yname xname dimername
plt.savefig('/content/drive/MyDrive/Colab Notebooks/res_data/dimers/'+str(yname)+'_'+str(xname)+'_'+str(dimername), bbox_inches='tight', dpi=300 )
you can save as
/content/drive/MyDrive/Colab Notebooks/res_data/dimers/2d_epsi_gamma_AU_new.dat