What if you did something like this:

```python

class Conversion: def init(self, args, *kwargs): "Put whatever settings you need here"

def python(self, row, column, value): # not sure on args here
    "Python step to transform value"
    return value

def sql(self, row, column, value):
    "Return the actual sql that goes in the insert/update step, and maybe params"
    # value is the return of self.python()
    return value, []

```

This way, you're always passing an instance, which has methods that do the conversion. (Or you're passing a SQL string, as you would now.) The __init__ could take column names, or SRID, or whatever other setup state you need per row, but the row is getting processed with the python and sql methods (or whatever you want to call them). This is pretty rough, so do what you will with names and args and such.

You'd then use it like this:

```python

subclass might be unneeded here, if methods are present

class LngLatConversion(Conversion): def init(self, x="longitude", y="latitude"): self.x = x self.y = y

def python(self, row, column, value):
    x = row[self.x]
    y = row[self.y]
    return x, y

def sql(self, row, column, value):
    # value is now a tuple, returned above
    s = "GeomFromText(POINT(? ?))"
    return s, value

table.insert_all(rows, conversions={"point": LngLatConversion("lng", "lat"))} ```

I haven't thought through all the implementation details here, and it'll probably break in ways I haven't foreseen, but wanted to get this idea out of my head. Hope it helps.