[SPARK-3309] [PySpark] Put all public API in __all__

Put all public API in __all__, also put them all in pyspark.__init__.py, then we can got all the documents for public API by `pydoc pyspark`. It also can be used by other programs (such as Sphinx or Epydoc) to generate only documents for public APIs.

Author: Davies Liu <davies.liu@gmail.com>

Closes #2205 from davies/public and squashes the following commits:

c6c5567 [Davies Liu] fix message
f7b35be [Davies Liu] put SchemeRDD, Row in pyspark.sql module
7e3016a [Davies Liu] add __all__ in mllib
6281b48 [Davies Liu] fix doc for SchemaRDD
6caab21 [Davies Liu] add public interfaces into pyspark.__init__.py

1 files changed, 14 insertions, 10 deletions

diff --git a/python/pyspark/broadcast.py b/python/pyspark/broadcast.py
index 675a2fcd2f..5c7c9cc161 100644
--- a/python/pyspark/broadcast.py
+++ b/python/pyspark/broadcast.py
@@ -31,6 +31,10 @@ import os
 
 from pyspark.serializers import CompressedSerializer, PickleSerializer
 
+
+__all__ = ['Broadcast']
+
+
 # Holds broadcasted data received from Java, keyed by its id.
 _broadcastRegistry = {}
 
@@ -59,11 +63,20 @@ class Broadcast(object):
         """
         self.bid = bid
         if path is None:
-            self.value = value
+            self._value = value
         self._jbroadcast = java_broadcast
         self._pickle_registry = pickle_registry
         self.path = path
 
+    @property
+    def value(self):
+        """ Return the broadcasted value
+        """
+        if not hasattr(self, "_value") and self.path is not None:
+            ser = CompressedSerializer(PickleSerializer())
+            self._value = ser.load_stream(open(self.path)).next()
+        return self._value
+
     def unpersist(self, blocking=False):
         self._jbroadcast.unpersist(blocking)
         os.unlink(self.path)
@@ -72,15 +85,6 @@ class Broadcast(object):
         self._pickle_registry.add(self)
         return (_from_id, (self.bid, ))
 
-    def __getattr__(self, item):
-        if item == 'value' and self.path is not None:
-            ser = CompressedSerializer(PickleSerializer())
-            value = ser.load_stream(open(self.path)).next()
-            self.value = value
-            return value
-
-        raise AttributeError(item)
-
 
 if __name__ == "__main__":
     import doctest