Converting string to float in Calculate Value for ModelBuilder?

Question

In ArcMap 10.2 I have created a nested model where I am iterating through some feature classes in order to get the minimum value of a specific field for each of them and then collect the outputs using the Collect Values Tool. The output is named Zminand for whatever reason it is a string.

Afterwards I want to get the minimum of these minima in order to use it as parameter in a following step of the main model.

I have tried to use the Calculate Value Tool as follows:

Expression:

lowest("%Zmin%")

Code Block:

def lowest(Zmin):
    Zmin.split(';')
    LowestLine = min(Zmin)
    return LowestLine

Data Type: Double

Unfortunately I get the following error message:

ValueError: invalid literal for float(): -129.8;-119.4;-118.9;-157.3

My knowledge of Python is not really deep, however the problem is obviously in the type of the input. I tried to split it into a list of strings by using Zmin.split(';')

before to convert it into floating points, but this is probably the wrong way and I do not know how to solve it.

Andy · Accepted Answer · 2019-01-16 14:22:08Z

1

You need to have an array of minima and then convert the individual values to floats before running min. Try this:

def lowest(Zmin):
    # assign the split string to an array
    minima = Zmin.split(';')

    # iterate through the array and convert each element to float
    for idx,value in enumerate(minima):
        minima[idx] = float(minima[idx])

    # determine the minimum value
    LowestLine = min(minima)
    return LowestLine

answered Jan 16, 2019 at 14:22

Andy

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