Issue #12288: Consider '0' and '0.0' as valid initialvalue for tkinter SimpleDialog.
diff --git a/Lib/tkinter/simpledialog.py b/Lib/tkinter/simpledialog.py
index 885804b..45302b4 100644
--- a/Lib/tkinter/simpledialog.py
+++ b/Lib/tkinter/simpledialog.py
@@ -282,7 +282,7 @@
         self.entry = Entry(master, name="entry")
         self.entry.grid(row=1, padx=5, sticky=W+E)
 
-        if self.initialvalue:
+        if self.initialvalue is not None:
             self.entry.insert(0, self.initialvalue)
             self.entry.select_range(0, END)