Implemented new particle diagnostics in picmi (#984)

* Implemented new particle diagnostics in picmi

* Cleaned up picmi adding new particle diagnostics

* In PICMI examples, use name option for diagnostics

* For travis, update ubuntu version to bionic

1 files changed, 12 insertions, 2 deletions

diff --git a/Python/pywarpx/Bucket.py b/Python/pywarpx/Bucket.py
index 714516fd3..7817f8f86 100644
--- a/Python/pywarpx/Bucket.py
+++ b/Python/pywarpx/Bucket.py
@@ -15,13 +15,23 @@ class Bucket(object):
     def __init__(self, instancename, **defaults):
         self._localsetattr('instancename', instancename)
         self._localsetattr('argvattrs', {})
-        self.argvattrs.update(defaults)
+        for name, value in defaults.items():
+            self.add_new_attr(name, value)
 
     def _localsetattr(self, name, value):
         object.__setattr__(self, name, value)
 
+    def add_new_attr(self, name, value):
+        """Names starting with "_" are make instance attributes.
+        Otherwise the attribute is added to the args list.
+        """
+        if name.startswith('_'):
+            self._localsetattr(name, value)
+        else:
+            self.argvattrs[name] = value
+
     def __setattr__(self, name, value):
-        self.argvattrs[name] = value
+        self.add_new_attr(name, value)
 
     def __getattr__(self, name):
         try: