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Switch - Examples of how to use Case When

Three ways to handle combination of Flow variables from Python and If switches

In one Python environment a Flow Variable for the usage in KNIME will be filled and the results will be used for two If switches.

if($${Ivar_py_value_switch}$$ >0) {return "bottom";}
else {return "top";}

URL: forum entry (27913) https://forum.knime.com/t/to-control-workflow-stream-using-if-switch-using-flow-variable-from-a-python-snippet/27913/2?u=mlauber71
URL: Meta Collection about KNIME and Python https://kni.me/w/AvjrddXKOIoZYLV3
URL: Vernalis KNIME Nodes https://hub.knime.com/vernalis/extensions/com.vernalis.knime.feature/latest
URL: DB SQLite - switch datase source based on a case when selection https://forum.knime.com/t/db-query-case-switch/63990/7?u=mlauber71
URL: META: A meta collection about Loops, Switches, Paths and Flow Variables in KNIME (and some ZIP files) https://hub.knime.com/-/spaces/-/latest/~CET0X2z2VY9oKlYN/

decide if
TOP or
BOTTOM

import knime.scripting.io as knio

import sys
import pandas as pd
# data processing, CSV file I/O (e.g. pd.read_csv)

input_table = knio.input_tables[0].to_pandas()

# this setting will be used as a flow variable in KNIME

# knio.flow_variables['var_py_value_switch'] = 0
knio.flow_variables['var_py_value_switch'] = 1

var_py_version = sys.version
var_py_version_pandas = pd.__version__

knio.flow_variables['var_py_version'] = sys.version
knio.flow_variables['var_py_version_pandas'] = pd.__version__

data = {'sys_version': [var_py_version],
'pandas_version': [var_py_version_pandas]
}

knio.output_tables[0] = knio.Table.from_pandas(input_table.copy())

# pass column names in the columns parameter
knio.output_tables[1] = knio.Table.from_pandas(pd.DataFrame(data))
Three ways to handle combination of Flow variables from Python and If switches

https://forum.knime.com/t/to-control-workflow-stream-using-if-switch-using-flow-variable-from-a-python-snippet/27913/2?u=mlauber71

In one Python environment a Flow Variable for the usage in KNIME will be filled and the results will be used for two If switches.

Blog: KNIME - Cases, Switches and Catching Errors

https://medium.com/p/5ab748cbeaa3

dummydata
Data Generator
v_result_switchSTART
IF Switch
result Python
End IF
v_result_switch"top"or "bottom"derived from Pythonvar_py_value_switch
Java Edit Variable (simple)
v_result_case_portset the active port via Integer Flow Variable
CASE Switch Start
bottom_result.xlsx
Excel Writer
CASE Switch End
v_result_case_portset the active port via Integer Flow Variable
CASE Switch Start
v_result_switchv_result_case_port
Variable Expression
bottom Python
Python Script
END
CASE Switch End
top Python
Python Script
CASE Switch Start
some Python script
Python Script
v_result_case_portwhich port should be activederived from Pythonvar_py_value_switchif($${Ivar_py_value_switch}$$ >0) {return 1;}else {return 0;}
Java Edit Variable (simple)
top Python
Python Script
bottom Python
Python Script
top Python
Python Script
top_result.xlsx
Excel Writer
result
CASE Switch End
bottom Python
Python Script
top Python
Python Script
bottom Python
Python Script

Nodes

Extensions

Links

Download

To use this workflow in KNIME, download it from the below URL and open it in KNIME:

Download Workflow
Created by: m_lauber
Created at: 2020-10-09
On NodePit since: 2024-11-15
Last update: 2026-02-18
Created with KNIME version: v5.9.0
Tags: pythonswitchifthenelsetopbottom

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