def _maybe_compose_deltas(old_delta: Delta,
new_delta: Delta) -> Optional[Delta]:
"""Combines new_delta onto old_delta if possible.
If the combination takes place, the function returns a new Delta that
should replace old_delta in the queue.
If the new_delta is incompatible with old_delta, the function returns None.
In this case, the new_delta should just be appended to the queue as normal.
"""
old_delta_type = old_delta.WhichOneof("type")
if old_delta_type == "add_block":
# We never replace add_block deltas, because blocks can have
# other dependent deltas later in the queue. For example:
#
# placeholder = st.empty()
# placeholder.columns(1)
# placeholder.empty()
#
# The call to "placeholder.columns(1)" creates two blocks, a parent
# container with delta_path (0, 0), and a column child with
# delta_path (0, 0, 0). If the final "placeholder.empty()" Delta
# is composed with the parent container Delta, the frontend will
# throw an error when it tries to add that column child to what is
# now just an element, and not a block.
return None
new_delta_type = new_delta.WhichOneof("type")
if new_delta_type == "new_element":
return new_delta
if new_delta_type == "add_block":
return new_delta
return None
def _maybe_compose_deltas(old_delta: Delta,
new_delta: Delta) -> Optional[Delta]:
"""Combines new_delta onto old_delta if possible.
If the combination takes place, the function returns a new Delta that
should replace old_delta in the queue.
If the new_delta is incompatible with old_delta, the function returns None.
In this case, the new_delta should just be appended to the queue as normal.
"""
old_delta_type = old_delta.WhichOneof("type")
if old_delta_type == "add_block":
# We never replace add_block deltas, because blocks can have
# other dependent deltas later in the queue. For example:
#
# placeholder = st.empty()
# placeholder.columns(1)
# placeholder.empty()
#
# The call to "placeholder.columns(1)" creates two blocks, a parent
# container with delta_path (0, 0), and a column child with
# delta_path (0, 0, 0). If the final "placeholder.empty()" Delta
# is composed with the parent container Delta, the frontend will
# throw an error when it tries to add that column child to what is
# now just an element, and not a block.
return None
new_delta_type = new_delta.WhichOneof("type")
if new_delta_type == "new_element":
return new_delta
if new_delta_type == "add_block":
return new_delta
if new_delta_type == "add_rows":
import streamlit.elements.legacy_data_frame as data_frame
# We should make data_frame.add_rows *not* mutate any of the
# inputs. In the meantime, we have to deepcopy the input that will be
# mutated.
composed_delta = copy.deepcopy(old_delta)
data_frame.add_rows(composed_delta,
new_delta,
name=new_delta.add_rows.name)
return composed_delta
# We deliberately don't handle the "arrow_add_rows" delta type. With Arrow,
# `add_rows` is a frontend-only operation.
return None
def _get_data_frame(delta: Delta, name: Optional[str] = None) -> DataFrame:
"""Extract the dataframe protobuf from a delta protobuf."""
delta_type = delta.WhichOneof("type")
if delta_type == "new_element":
element_type = delta.new_element.WhichOneof("type")
# Some element types don't support named datasets.
if name and element_type in ("data_frame", "table", "chart"):
raise ValueError("Dataset names not supported for st.%s" %
element_type)
if element_type in "data_frame":
return delta.new_element.data_frame
elif element_type in "table":
return delta.new_element.table
elif element_type == "chart":
return delta.new_element.chart.data
elif element_type == "vega_lite_chart":
chart_proto = delta.new_element.vega_lite_chart
if name:
return _get_or_create_dataset(chart_proto.datasets, name)
elif len(chart_proto.datasets) == 1:
# Support the case where the dataset name was randomly given by
# the charting library (e.g. Altair) and the user has no
# knowledge of it.
return chart_proto.datasets[0].data
else:
return chart_proto.data
# TODO: Support DeckGL. Need to figure out how to handle layer indices
# first.
elif delta_type == "add_rows":
if delta.add_rows.has_name and name != delta.add_rows.name:
raise ValueError('No dataset found with name "%s".' % name)
return delta.add_rows.data
else:
raise ValueError("Cannot extract DataFrame from %s." % delta_type)
