I am trying to run a calculation on a Pandas Dataframe and don’t understand why the direct calculation fails and the loop calculation works. The direct calculation works if I remove the math.sqrt function.

a, b and c are float constants.

This line fails:

grid['Conf'] = (-b + math.sqrt(b*b-4.0*a*(c-grid['Distance'])))/(2.0*a)

The error is

--> 185 raise TypeError(f"cannot convert the series to {converter}")

TypeError: cannot convert the series to <class 'float'>

But this works (incorrect results since the sqrt is removed):

grid['Conf'] = (-b + (b*b-4.0*a*(c-grid['Distance'])))/(2.0*a)

And this works (correct result but takes a long time to calculate):

for i in grid.index:
    grid['Conf'].iloc[i] = (-b + math.sqrt(b*b-4.0*a*(c-grid['Distance'].iloc[i])))/(2.0*a)