picamera2 init: Don't override LIBCAMERA_RPI_CONFIG_FILE if valid

If the environment variable already exists and points to a valid
file, keep it. This allows the config file to be user-specified
from outside the Python script.

Signed-off-by: Nick Hollinghurst <[email protected]>

Author: njhollinghurst

picamera2/__init__.py

@@ -19,6 +19,10 @@
 
 
 def _set_configuration_file(filename):
+    oldval = os.environ.get('LIBCAMERA_RPI_CONFIG_FILE')
+    if oldval is not None and os.path.isfile(oldval):
+        return
+
     platform_dir = "vc4" if get_platform() == Platform.VC4 else "pisp"
     dirs = [
         os.path.expanduser(
@@ -29,12 +33,10 @@ def _set_configuration_file(filename):
 
     for directory in dirs:
         file = os.path.join(directory, filename)
-
         if os.path.isfile(file):
             os.environ['LIBCAMERA_RPI_CONFIG_FILE'] = file
             break
 
-
 _set_configuration_file("rpi_apps.yaml")