fix python syntax issue (#51658)

python/paddle/fluid/core.py

@@ -481,25 +481,25 @@ def _set_prim_forward_blacklist(ops=None):
 
 def _set_prim_backward_enabled(value):
     __set_bwd_prim_enabled(bool(value))
-    if os.getenv("FLAGS_prim_log") is "1":
+    if os.getenv("FLAGS_prim_log") == "1":
         print("backward prim enabled: ", bool(_is_bwd_prim_enabled()))
 
 
 def _set_prim_forward_enabled(value):
     __set_fwd_prim_enabled(bool(value))
-    if os.getenv("FLAGS_prim_log") is "1":
+    if os.getenv("FLAGS_prim_log") == "1":
         print("forward prim enabled: ", bool(_is_fwd_prim_enabled()))
 
 
 def set_prim_eager_enabled(value):
     __set_eager_prim_enabled(bool(value))
-    if os.getenv("FLAGS_prim_log") is "1":
+    if os.getenv("FLAGS_prim_log") == "1":
         print("eager prim enabled: ", bool(_is_eager_prim_enabled()))
 
 
 def _set_prim_all_enabled(value):
     __set_all_prim_enabled(bool(value))
-    if os.getenv("FLAGS_prim_log") is "1":
+    if os.getenv("FLAGS_prim_log") == "1":
         print(
             "all prim enabled: ",
             bool(_is_fwd_prim_enabled() and _is_bwd_prim_enabled()),
@@ -509,7 +509,7 @@ def _set_prim_all_enabled(value):
 def __sync_prim_backward_status():
     flag_value = os.getenv("FLAGS_prim_backward")
     if flag_value is None:
-        if os.getenv("FLAGS_prim_log") is "1":
+        if os.getenv("FLAGS_prim_log") == "1":
             print("backward prim enabled: ", bool(_is_bwd_prim_enabled()))
     else:
         __sync_stat_with_flag("FLAGS_prim_backward")
@@ -518,7 +518,7 @@ def __sync_prim_backward_status():
 def __sync_prim_forward_status():
     flag_value = os.getenv("FLAGS_prim_forward")
     if flag_value is None:
-        if os.getenv("FLAGS_prim_log") is 1:
+        if os.getenv("FLAGS_prim_log") == "1":
             print("forward prim enabled: ", bool(_is_fwd_prim_enabled()))
     else:
         __sync_stat_with_flag("FLAGS_prim_forward")