remove f-strings for python 3.5 compatibility (#854)

baselines/common/mpi_util.py

@@ -123,7 +123,7 @@ def mpi_weighted_mean(comm, local_name2valcount):
                     val = float(val)
                 except ValueError:
                     if comm.rank == 0:
-                        warnings.warn(f'WARNING: tried to compute mean on non-float {name}={val}')
+                        warnings.warn('WARNING: tried to compute mean on non-float {}={}'.format(name, val))
                 else:
                     name2sum[name] += val * count
                     name2count[name] += count

baselines/common/running_mean_std.py

@@ -177,7 +177,7 @@ def profile_tf_runningmeanstd():
     outfile = '/tmp/timeline.json'
     with open(outfile, 'wt') as f:
         f.write(chrome_trace)
-    print(f'Successfully saved profile to {outfile}. Exiting.')
+    print('Successfully saved profile to {}. Exiting.'.format(outfile))
     exit(0)
     '''
 

baselines/common/test_mpi_util.py

@@ -17,7 +17,7 @@ def test_mpi_weighted_mean():
         d = mpi_util.mpi_weighted_mean(comm, name2valcount)
         correctval = {'a' : (10 * 2 + 19) / 3.0, 'b' : 20, 'c' : 42}
         if comm.rank == 0:
-            assert d == correctval, f'{d} != {correctval}'
+            assert d == correctval, '{} != {}'.format(d, correctval)
 
         for name, (val, count) in name2valcount.items():
             for _ in range(count):

baselines/run.py

@@ -232,7 +232,7 @@ def main(args):
             env.render()
             done = done.any() if isinstance(done, np.ndarray) else done
             if done:
-                print(f'episode_rew={episode_rew}')
+                print('episode_rew={}'.format(episode_rew))
                 episode_rew = 0
                 obs = env.reset()