diff --git a/python/pip.bzl b/python/pip.bzl
index 237b7d2baa..780c05a875 100644
--- a/python/pip.bzl
+++ b/python/pip.bzl
@@ -13,6 +13,20 @@
 # limitations under the License.
 """Import pip requirements into Bazel."""
 
+
+def python(repository_ctx):
+    if "BAZEL_PYTHON" in repository_ctx.os.environ:
+        return repository_ctx.os.environ.get("BAZEL_PYTHON")
+
+    python_path = repository_ctx.which("python")
+    if not python_path:
+      python_path = repository_ctx.which("python.exe")
+    if python_path:
+        return python_path
+
+    fail("rules_python requires a python interpreter installed. " +
+         "Please set BAZEL_PYTHON, or put it on your path.")
+
 def _pip_import_impl(repository_ctx):
   """Core implementation of pip_import."""
 
@@ -24,7 +38,7 @@ def _pip_import_impl(repository_ctx):
 
   # To see the output, pass: quiet=False
   result = repository_ctx.execute([
-    "python", repository_ctx.path(repository_ctx.attr._script),
+    python(repository_ctx), repository_ctx.path(repository_ctx.attr._script),
     "--name", repository_ctx.attr.name,
     "--input", repository_ctx.path(repository_ctx.attr.requirements),
     "--output", repository_ctx.path("requirements.bzl"),
diff --git a/python/whl.bzl b/python/whl.bzl
index 496755671f..372c4acc63 100644
--- a/python/whl.bzl
+++ b/python/whl.bzl
@@ -13,11 +13,24 @@
 # limitations under the License.
 """Import .whl files into Bazel."""
 
+def python(repository_ctx):
+    if "BAZEL_PYTHON" in repository_ctx.os.environ:
+        return repository_ctx.os.environ.get("BAZEL_PYTHON")
+
+    python_path = repository_ctx.which("python")
+    if not python_path:
+      python_path = repository_ctx.which("python.exe")
+    if python_path:
+        return python_path
+
+    fail("rules_docker requires a python interpreter installed. " +
+         "Please set BAZEL_PYTHON, or put it on your path.")
+
 def _whl_impl(repository_ctx):
   """Core implementation of whl_library."""
 
   args = [
-    "python",
+    python(repository_ctx),
     repository_ctx.path(repository_ctx.attr._script),
     "--whl", repository_ctx.path(repository_ctx.attr.whl),
     "--requirements", repository_ctx.attr.requirements,