Source code for node_json2table
# This file is part of Sympathy for Data.
# Copyright (c) 2018, Combine Control Systems AB
#
# Sympathy for Data is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, version 3 of the License.
#
# Sympathy for Data is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Sympathy for Data. If not, see <http://www.gnu.org/licenses/>.
from sympathy.api import node as synode
from sympathy.api import node_helper
from sympathy.api.nodeconfig import Port, Ports, Tag, Tags
from sympathy.api.exceptions import SyDataError
from sylib.json_table import (JsonTableWidget, JsonTable,
add_jsontable_parameters, TABLE_KIND)
def parameters_base():
parameters = synode.parameters()
add_jsontable_parameters(parameters)
return parameters
[docs]class JsonToTable(synode.Node):
"""
Convert a JSON file to a Table
There are two kinds of tables that can be created:
* Single row – where the JSON structure is simply flattened
* Multiple rows - where the JSON structure is recursively expanded to
create several rows
If a single-row table is created, there is an option to minimize the
column names to remove unnecessary path information from the JSON keys.
For example from the JSON:
.. code-block:: python
{
"version":"1.0",
"software":"sfd",
"items" : {
"a":"1",
"b":"2",
"c":"3"
}
}
we can create the following single-row table
.. code-block:: python
version software items.a items.b items.c
----------------------------------------------------
1.0 sfd 1 2 3
and the column names can be *minimized* to
.. code-block:: python
version software a b c
-------------------------------------
1.0 sfd 1 2 3
If a multiple rows-table is created, the recursive algorithm might identify
keys and therefore columns that are lacking some values. One can choose to
fill in the missing values with a **empty string**, a **nan** string or
**mask** the value.
For example from the JSON:
.. code-block:: python
{
"version":"1.0",
"software":"sfd",
"items" : [
{
"a":"1",
"b":"2",
"c":"3"
},
{
"a":"67",
"b":"77",
"d":"97"
}
]
}
we can create the following multiple-rows table
.. code-block:: python
version software a b c d
-------------------------------------------
1.0 sfd 1 2 3 ---
1.0 sfd 67 77 --- 97
where the ``c`` column is masked in the second row and the ``d``
column is masked in the first row.
If the algorithm that creates tnhe multi-row table fails to produce
the desired table, it might be worth using other nodes to remove,
select or split the JSON structure on some key.
"""
name = 'JSON to Table'
author = 'Samuel Genheden'
version = '0.1'
icon = 'json2table.svg'
tags = Tags(Tag.DataProcessing.Convert)
nodeid = 'org.sysess.sympathy.data.json.jsontotable'
inputs = Ports([Port.Json('Input JSON object', name='input')])
outputs = Ports([Port.Table('Output table', name='output')])
parameters = parameters_base()
def exec_parameter_view(self, node_context):
return JsonTableWidget(node_context.parameters)
def execute(self, node_context):
table_kind = node_context.parameters['table_kind'].value
min_col_names = node_context.parameters['minimize_col_names'].value
nomask = node_context.parameters['nomask'].value
tbl = JsonTable(node_context.input[0])
if not tbl.is_group():
value = node_context.input[0].get()
raise SyDataError(
f'Inputs must be list or dict, it is '
f'{value} ({type(value).__name__}).')
if table_kind == TABLE_KIND["SINGLE"]:
node_context.output[0].source(
tbl.create_single_row_table(min_col_names))
else:
node_context.output[0].source(
tbl.create_multiple_rows_table(nomask))
[docs]@node_helper.list_node_decorator(['input'], ['output'])
class JsonsToTables(JsonToTable):
name = "JSONs to Tables"
nodeid = "org.sysess.sympathy.data.json.jsonstotables"
