topic in a pyt (python toolbox): How do I make a boolean parameter default False??? in Python Questions

in a pyt (python toolbox): How do I make a boolean parameter default False???

MartinHvidberg — Fri, 26 Sep 2014 13:42:20 GMT

In a .pyt I can define parameters as described in :

I have created a boolean parameter, the code snippet is as follow:

	def getParameterInfo(self):
	"""Define parameter definitions"""

... some other parameters ...

	# 3. Overwrite
	param3 = arcpy.Parameter(
	displayName="Overwrite Existing OBJ",
	name="Overwrite",
	datatype="GPBoolean",
	parameterType="Required",
	direction="Input")

The parameter works, but it anoys me that it defaults to True, I would like it to default to False.

v.h. Martin

Re: in a pyt (python toolbox): How do I make a boolean parameter default False???

TimothyHales — Sun, 12 Dec 2021 04:43:29 GMT

You can set the default value by setting the value like this:


param3 = arcpy.Parameter(


     displayName="Overwrite Existing OBJ",


     name="Overwrite",


     datatype="GPBoolean",


     parameterType="Required",


     direction="Input")  






param3.value = "False"

Re: in a pyt (python toolbox): How do I make a boolean parameter default False???

curtvprice — Sat, 27 Sep 2014 04:07:13 GMT

Right on, Tim.

There are more details (and examples) in the help page on this topic:

Defining parameters in a Python toolbox: ‌/ Setting default values for a parameter

Another wrinkle with booleans is the use of keywords, so the script tool's dialog box (and arcpy) will support a pick list of keywords.

From the same help page:

A Value List can be used for Boolean data types. For Boolean data types, the Value List contains two values: the true value and false value. The true value is always the first value in the list. These values are used in the command line for specifying the value.

param3.filter.list = ["OVERWRITE", "NO_OVERWRITE"]
param3.value = False

Re: in a pyt (python toolbox): How do I make a boolean parameter default False???

curtvprice — Mon, 29 Sep 2014 00:59:02 GMT

Timothy Hales‌ and Martin Hvidberg‌ - wondering about:

param3.value = "False"

as Python bool ("False") is true (ie the string is "False" is non-empty so it is considered True in value. The parameter object may be converting it from "False" to False but I'd check to be sure.

Re: in a pyt (python toolbox): How do I make a boolean parameter default False???

TimothyHales — Mon, 29 Sep 2014 01:32:00 GMT

Valid concern there. I just tested this, and the string and the raw value both are seen correctly.

def getParameterInfo(self):
        """Define parameter definitions"""
        param2 = arcpy.Parameter(
             displayName="False String",
             name="FalseString",
             datatype="GPBoolean",
             parameterType="Required",
             direction="Input")  
        param2.value = "False"
        param3 = arcpy.Parameter(
             displayName="False",
             name="False",
             datatype="GPBoolean",
             parameterType="Required",
             direction="Input")  
        param3.value = False
        param4 = arcpy.Parameter(
             displayName="True String",
             name="TrueString",
             datatype="GPBoolean",
             parameterType="Required",
             direction="Input")  
        param4.value = "True"
        param5 = arcpy.Parameter(
             displayName="True",
             name="True",
             datatype="GPBoolean",
             parameterType="Required",
             direction="Input")  
        param5.value = True
        params = [param2, param3, param4, param5]
        return params

Re: in a pyt (python toolbox): How do I make a boolean parameter default False???

curtvprice — Mon, 29 Sep 2014 22:11:01 GMT

def execute(self, parameters, messages):
    """The source code of the tool."""
    arcpy.AddMessage([k.value for k in parameters])
    return

Executing: Tool false false true true
Start Time: Mon Sep 29 16:09:23 2014
Running script Tool...
[False, False, True, True]
Completed script Tool...
Succeeded at Mon Sep 29 16:09:23 2014 (Elapsed Time: 0.00 seconds)

Yes, indeed, everything gets interpreted through its string representation, which I bet is case insensitive ("false" is interpreted by arcpy the same as "False")