missing_data_3.py

import pandas as pd

missing_value_formats = ["n.a.","?","NA","n/a", "na", "--"]
df = pd.read_csv("employees.csv", na_values = missing_value_formats)

def make_int(i):
    try:
        return int(i)
    except:
        return pd.np.nan

# apply make_int function to the entire series using map
df['Salary'] = df['Salary'].map(make_int)
print(df['Salary'].head())