TypeError: float() argument must be a string or a number, not 'function'
a generic way to convert pandas column to numeric dtype:

df['col_name'] = pd.to_numeric(df['col_name'], errors='coerce')


this will replace all values, that couldn't be converted to numeric values with NaN's (Not a Number).

PS you may want to analyze how and why do you have a reference to a lambda function in your cells. Fixing the source of that problem would be a more appropriate solution.