Pandas Dataframe: Multiplying Two Columns

I believe that your ActualSalary column is a mix of strings and integers. That is the only way I've been able to recreate your error:

df = pd.DataFrame(
    {'ActualSalary': ['44600', '58,000.00', '70,000.00', 17550, 34693, 15674],
     'FTE': [1, 1, 1, 1, 1, 0.4]})

>>> df['ActualSalary'].str.replace(',', '').astype(float) * df['FTE']
0    44600.0
1    58000.0
2    70000.0
3        NaN
4        NaN
5        NaN
dtype: float64

The issue arises when you try to remove the commas:

>>> df['ActualSalary'].str.replace(',', '')
0       44600
1    58000.00
2    70000.00
3         NaN
4         NaN
5         NaN
Name: ActualSalary, dtype: object

First convert them to strings, before converting back to floats.

fte_salary = (
    df['ActualSalary'].astype(str).str.replace(',', '')  # Remove commas in string, e.g. '55,000.00' -> '55000.00'
    .astype(float)  # Convert string column to floats.
    .mul(df['FTE'])  # Multiply by new salary column by Full-Time-Equivalent (FTE) column.
)
>>> df.assign(FTESalary=fte_salary)  # Assign new column to dataframe.
      ActualSalary  FTE  FTESalary
    0        44600  1.0    44600.0
    1    58,000.00  1.0    58000.0
    2    70,000.00  1.0    70000.0
    3        17550  1.0    17550.0
    4        34693  1.0    34693.0
    5        15674  0.4     6269.6