Override JSONEncoder.iterencode

We do this to handle NaN, Inf, and -Inf

Author: theengineear

plotly/utils.py

@@ -119,8 +119,72 @@ class PlotlyJSONEncoder(json.JSONEncoder):
 
     See PlotlyJSONEncoder.default for more implementation information.
 
+    Additionally, this encoder overrides nan functionality so that 'Inf',
+    'NaN' and '-Inf' encode to 'null'. Which is stricter JSON than the Python
+    version.
+
     """
 
+    # we want stricter JSON, so convert NaN, Inf, -Inf --> 'null'
+    nan_str = inf_str = neg_inf_str = 'null'
+
+    # uses code from official python json.encoder module. Same licence applies.
+    def iterencode(self, o, _one_shot=False):
+        """
+        Encode the given object and yield each string
+        representation as available.
+
+        For example::
+
+            for chunk in JSONEncoder().iterencode(bigobject):
+                mysocket.write(chunk)
+
+        """
+        if self.check_circular:
+            markers = {}
+        else:
+            markers = None
+        if self.ensure_ascii:
+            _encoder = json.encoder.encode_basestring_ascii
+        else:
+            _encoder = json.encoder.encode_basestring
+        if self.encoding != 'utf-8':
+            def _encoder(o, _orig_encoder=_encoder, _encoding=self.encoding):
+                if isinstance(o, str):
+                    o = o.decode(_encoding)
+                return _orig_encoder(o)
+
+        def floatstr(o, allow_nan=self.allow_nan,
+                     _repr=json.encoder.FLOAT_REPR, _inf=json.encoder.INFINITY,
+                     _neginf=-json.encoder.INFINITY):
+            # Check for specials.  Note that this type of test is processor
+            # and/or platform-specific, so do tests which don't depend on the
+            # internals.
+
+            # *any* two NaNs are not equivalent (even to itself) try:
+            # float('NaN') == float('NaN')
+            if o != o:
+                text = self.nan_str
+            elif o == _inf:
+                text = self.inf_str
+            elif o == _neginf:
+                text = self.neg_inf_str
+            else:
+                return _repr(o)
+
+            if not allow_nan:
+                raise ValueError(
+                    "Out of range float values are not JSON compliant: " +
+                    repr(o))
+
+            return text
+
+        _iterencode = json.encoder._make_iterencode(
+                markers, self.default, _encoder, self.indent, floatstr,
+                self.key_separator, self.item_separator, self.sort_keys,
+                self.skipkeys, _one_shot)
+        return _iterencode(o, 0)
+
     def default(self, obj):
         """
         Accept an object (of unknown type) and try to encode with priority: