diff --git a/notebooks/one_time.ipynb b/notebooks/one_time.ipynb
index 20ae67415..b5cc7da6f 100644
--- a/notebooks/one_time.ipynb
+++ b/notebooks/one_time.ipynb
@@ -95,7 +95,7 @@
     "M.set(common_settings)\n",
     "M.compute()\n",
     "derived = M.get_current_derived_parameters(['z_rec','tau_rec','conformal_age'])\n",
-    "#print derived.viewkeys()\n",
+    "#print(derived.keys())\n",
     "z_rec = derived['z_rec']\n",
     "z_rec = int(1000.*z_rec)/1000. # round down at 4 digits after coma\n",
     "M.struct_cleanup()  # clean output\n",
@@ -111,7 +111,7 @@
     "# load transfer functions at recombination\n",
     "#\n",
     "one_time = M.get_transfer(z_rec)\n",
-    "print one_time.viewkeys()\n",
+    "print(one_time.keys())\n",
     "k = one_time['k (h/Mpc)']\n",
     "Theta0 = 0.25*one_time['d_g']\n",
     "phi = one_time['phi']\n",
@@ -129,7 +129,7 @@
     "# Hubble crossing (k = 2 pi a H), sound horizon crossing (k = 2pi / rs)\n",
     "#\n",
     "background = M.get_background() # load background table\n",
-    "#print background.viewkeys()\n",
+    "#print(background.keys())\n",
     "#\n",
     "background_tau = background['conf. time [Mpc]'] # read confromal times in background table\n",
     "background_z = background['z'] # read redshift\n",