Intern static string
Use float constructors instead of magic code for float constants
diff --git a/Modules/_json.c b/Modules/_json.c
index deee1e3..ea6d66f 100644
--- a/Modules/_json.c
+++ b/Modules/_json.c
@@ -215,7 +215,7 @@
         ustr = PyUnicode_FromUnicode(&c, 0);
     }
     if (joinstr == NULL) {
-        joinstr = PyString_FromString("join");
+        joinstr = PyString_InternFromString("join");
     }
     if (joinstr == NULL || ustr == NULL) {
         return NULL;