Passing conditional statements into arcpy.da.UpdateCursor

Question

How do you pass conditional statements from a list into a data access module update cursor?

I am using ArcGIS v10.3.1.

a = r"...\Default.gdb\New_Shapefile"
ConList = ["r[1] >= 1"]
with arcpy.da.UpdateCursor(a, ["Id", "apples"]) as uCur:
    for r in uCur:
        if ConList[0]:
            r[0] = 99
            uCur.updateRow(r)

Result is shown, highlighted rows should hold the pre-existing value of zero.

Answer 1

Without rewriting your code, you can use eval() to evaluate your expression string as Python.

a = r"...\Default.gdb\New_Shapefile"
ConList = ["r[1] >= 1"]
with arcpy.da.UpdateCursor(a, ["Id", "apples"]) as uCur:
    for r in uCur:
        if eval(ConList[0]): # evaluates your expression
            r[0] = 99
            uCur.updateRow(r)

Answer 2

To clarify so you don't repeat that problem, the problem lies with your if statement, as it will always be True as written. Example:

>>> ConList = ["a = b"]
>>> if ConList[0]: print true

The above prints "true" but should not print anything. Your if statement simply evaluates whether or not there is a value in ConList[0]; it isn't using the expression within it.

The above advice of a function is the way to go.