Fix print for py2 (#662)

Author: wanghaoshuang

demo/dygraph/pruning/eval.py

@@ -105,7 +105,7 @@ def eval(args):
     ratios = {}
     for param in params:
         ratios[param] = args.pruned_ratio
-    print(f"ratios: {ratios}")
+    print("ratios: {}".format(ratios))
     pruner.prune_vars(ratios, [0])
 
     model = paddle.Model(net, inputs, labels)

demo/dygraph/pruning/export_model.py

@@ -86,7 +86,7 @@ def export(args):
     ratios = {}
     for param in params:
         ratios[param] = args.pruned_ratio
-    print(f"ratios: {ratios}")
+    print("ratios: {}".format(ratios))
     pruner.prune_vars(ratios, [0])
 
     param_state_dict = paddle.load(args.checkpoint + ".pdparams")

demo/dygraph/pruning/train.py

@@ -171,7 +171,7 @@ def compress(args):
 
     for param in net.parameters():
         if "conv2d" in param.name:
-            print(f"{param.name}\t{param.shape}")
+            print("{}\t{}".format(param.name, param.shape))
 
     net.train()
     model = paddle.Model(net, inputs, labels)