.onLoad set backend

Author: t-kalinowski

R/package.R

@@ -52,7 +52,7 @@ keras <- NULL
 .onLoad <- function(libname, pkgname) {
 
   # tensorflow:::.onLoad() registers some reticulate class filter hooks
-  # we need to identify tensors reliably.
+  # we need to identify tensorflow tensors reliably.
   requireNamespace("tensorflow", quietly = TRUE)
   maybe_register_S3_methods()
 
@@ -61,13 +61,17 @@ keras <- NULL
   if (!is.null(keras_python))
     Sys.setenv(RETICULATE_PYTHON = keras_python)
 
-  # default backend is tensorflow for now
-  # the tensorflow R package calls `py_require()` to ensure GPU is usable on Linux
   py_require(c(
     "keras", "pydot", "scipy", "pandas", "Pillow",
-    "ipython", "tensorflow_datasets"
+    "ipython" #, "tensorflow_datasets"
   ))
 
+  # default backend is tensorflow for now
+  # the tensorflow R package calls `py_require()` to ensure GPU is usable on Linux
+  # use_backend() includes py_require(action = "remove") calls to undo
+  # what tensorflow:::.onLoad() did. Keep them in sync!
+  use_backend(Sys.getenv("KERAS_BACKEND", "tensorflow"))
+
   # delay load keras
   try(keras <<- import("keras", delay_load = list(