use local variable everywhere

run.bat

@@ -1,15 +1,15 @@
 @ECHO off
 
-:: Check python installation
-python.exe --version > NUL
-
-:: Clean potential error or python version
-CLS
-
 :: Variables
 SET "pipR=pip install -r .\requirements.txt"
 SET "py=python.exe"
 
+:: Check python installation
+%py% --version > NUL
+
+:: Clean potential error or python version
+CLS
+
 IF errorlevel 1 (
     ECHO Installation of Python not found, installation...
 
@@ -28,7 +28,7 @@ IF errorlevel 1 (
     %py% -m %pipR%
 ) ELSE (
     :: Check dependencies
-    python.exe -m %pipR% > NUL
+    %py% -m %pipR% > NUL
 )
 
 :: Run app