arcpy - Unsupported Operand Type for Field Query

Following on from Correct SQL expression for SelectbyAttribute Tool, I have my code:

import arcpy


plantFile = r"U:\Users\K\Plants.shp"
field = "UID"

arcpy.MakeFeatureLayer_management (plantFile, "plant_temp")
expression = round("UID" / 2, 0) <> "UID" / 2
arcpy.SelectLayerByAttribute_management("plant_temp", "NEW_SELECTION", expression)

I encounter -- TypeError: unsupported operand type(s) for /: 'str' and 'int'

"UID" is a long integer field, so I'm not understanding why this is happening. I've looked up methods for changing types for individual values, but not for an entire field. I will also be running this on over 20,000 records, so processing time is a concern.

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EDIT I applied the suggested expression expression = '''round("UID" / 2, 0) <> "UID" / 2'''

which returned ExecuteError: ERROR 000358: Invalid expression