Rework iteration to only retrieve the key, enable getting the value of the current key.

Use common active_key, fix finish(), etc.
Rename example and use the key iteration.
Additional tests.

Author: Neradoc

adafruit_json_stream.py

@@ -154,7 +154,7 @@ def __init__(self, stream):
         self.finish_char = ""
 
     def finish(self):
-        """Consume all of the characters for this list from the stream."""
+        """Consume all of the characters for this container from the stream."""
         if not self.done:
             if self.active_child:
                 self.active_child.finish()
@@ -163,7 +163,8 @@ def finish(self):
         self.done = True
 
     def as_object(self):
-        """Consume all of the characters for this list from the stream and return as an object."""
+        """Consume all of the characters for this container from the stream
+        and return as an object."""
         if self.has_read:
             raise BufferError("Object has already been partly read.")
 
@@ -207,10 +208,17 @@ class TransientObject(Transient):
     def __init__(self, stream):
         super().__init__(stream)
         self.finish_char = "}"
-        self.active_child_key = None
+        self.active_key = None
+
+    def finish(self):
+        """Consume all of the characters for this container from the stream."""
+        if self.active_key and not self.active_child:
+            self.done = self.data.fast_forward(",")
+            self.active_key = None
+        super().finish()
 
     def __getitem__(self, key):
-        if self.active_child and self.active_child_key == key:
+        if self.active_child and self.active_key == key:
             return self.active_child
 
         self.has_read = True
@@ -219,12 +227,16 @@ def __getitem__(self, key):
             self.active_child.finish()
             self.done = self.data.fast_forward(",")
             self.active_child = None
-            self.active_child_key = None
+            self.active_key = None
         if self.done:
             raise KeyError(key)
 
         while not self.done:
-            current_key = self.data.next_value(":")
+            if self.active_key:
+                current_key = self.active_key
+                self.active_key = None
+            else:
+                current_key = self.data.next_value(":")
             if current_key is None:
                 self.done = True
                 break
@@ -234,43 +246,44 @@ def __getitem__(self, key):
                     self.done = True
                 if isinstance(next_value, Transient):
                     self.active_child = next_value
-                    self.active_child_key = key
+                    self.active_key = key
                 return next_value
             self.done = self.data.fast_forward(",")
         raise KeyError(key)
 
     def __iter__(self):
         return self
 
-    def _next_item(self):
-        """Return the next item as a (key, value) pair, regardless of key."""
-        if self.active_child:
-            self.active_child.finish()
+    def _next_key(self):
+        """Return the next item's key, without consuming the value."""
+        if self.active_key:
+            if self.active_child:
+                self.active_child.finish()
+                self.active_child = None
             self.done = self.data.fast_forward(",")
-            self.active_child = None
+            self.active_key = None
         if self.done:
             raise StopIteration()
 
+        self.has_read = True
+
         current_key = self.data.next_value(":")
         if current_key is None:
             self.done = True
             raise StopIteration()
 
-        next_value = self.data.next_value(",")
-        if self.data.last_char == ord("}"):
-            self.done = True
-        if isinstance(next_value, Transient):
-            self.active_child = next_value
-        return (current_key, next_value)
+        self.active_key = current_key
+        return current_key
 
     def __next__(self):
-        return self._next_item()[0]
+        return self._next_key()
 
     def items(self):
-        """Return iterator ine the dictionary’s items ((key, value) pairs)."""
+        """Return iterator in the dictionary’s items ((key, value) pairs)."""
         try:
             while not self.done:
-                yield self._next_item()
+                key = self._next_key()
+                yield (key, self[key])
         except StopIteration:
             return
 

examples/json_stream_advanced.py renamed to examples/json_stream_local_file_advanced.py

@@ -23,31 +23,52 @@ def iter_content(self, chunk_size):
 obj = json_stream.load(FakeResponse(f).iter_content(32))
 
 
-def find_keys(obj, keys):
+def find_keys(haystack, keys):
     """If we don't know the order in which the keys are,
     go through all of them and pick the ones we want"""
-    out = dict()
+    out = {}
     # iterate on the items of an object
-    for key, value in obj.items():
+    for key in haystack:
         if key in keys:
+            # retrieve the value only if needed
+            value = haystack[key]
             # if it's a sub object, get it all
-            if isinstance(value, json_stream.Transient):
+            if hasattr(value, "as_object"):
                 value = value.as_object()
             out[key] = value
     return out
 
+
+months = [
+    "January",
+    "February",
+    "March",
+    "April",
+    "May",
+    "June",
+    "July",
+    "August",
+    "September",
+    "October",
+    "November",
+    "December",
+]
+
+
 def time_to_date(stamp):
     tt = time.localtime(stamp)
-    month = ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"][tt.tm_mon]
+    month = months[tt.tm_mon]
     return f"{tt.tm_mday:2d}th of {month}"
 
+
 def ftoc(temp):
     return (temp - 32) * 5 / 9
 
+
 currently = obj["currently"]
 print("Currently:")
-print("    ", time_to_date(currently["time"]))
-print("    ", currently["icon"])
+print(" ", time_to_date(currently["time"]))
+print(" ", currently["icon"])
 
 # iterate on the content of a list
 for i, day in enumerate(obj["daily"]["data"]):
@@ -56,7 +77,7 @@ def ftoc(temp):
     print(
         f'On {date}: {day_items["summary"]},',
         f'Max: {int(day_items["temperatureHigh"])}F',
-        f'({int(ftoc(day_items["temperatureHigh"]))}C)'
+        f'({int(ftoc(day_items["temperatureHigh"]))}C)',
     )
 
     if i > 4:

tests/test_json_stream.py

@@ -696,6 +696,18 @@ def test_iterating_keys(dict_with_keys):
     assert output == ["field_1", "field_2", "field_3"]
 
 
+def test_iterating_keys_get(dict_with_keys):
+    """Iterate through keys of a simple object and get values."""
+
+    the_dict = json.loads(dict_with_keys)
+
+    bytes_io_chunk = BytesChunkIO(dict_with_keys.encode())
+    stream = adafruit_json_stream.load(bytes_io_chunk)
+    for key in stream:
+        value = stream[key]
+        assert value == the_dict[key]
+
+
 def test_iterating_items(dict_with_keys):
     """Iterate through items of a simple object."""
 
@@ -723,3 +735,28 @@ def test_iterating_items_after_get(dict_with_keys):
     assert stream["field_1"] == 1
     output = list(stream.items())
     assert output == [("field_2", 2), ("field_3", 3)]
+
+
+def test_iterating_complex_dict(complex_dict):
+    """Mix iterating over items of objects in objects in arrays."""
+
+    names = ["one", "two", "three", "four"]
+    sub_values = [None, "two point one", "three point one", None]
+
+    stream = adafruit_json_stream.load(BytesChunkIO(complex_dict.encode()))
+
+    thing_num = 0
+    for (index, item) in enumerate(stream.items()):
+        key, a_list = item
+        assert key == f"list_{index+1}"
+        for thing in a_list:
+            assert thing["dict_name"] == names[thing_num]
+            for sub_key in thing["sub_dict"]:
+                # break after getting a key with or without the value
+                # (testing finish() called from the parent list)
+                if sub_key == "sub_dict_name":
+                    if thing_num in {1, 2}:
+                        value = thing["sub_dict"][sub_key]
+                        assert value == sub_values[thing_num]
+                    break
+            thing_num += 1