Switch-case like structure in python
<p>I have the following function that I've made which takes a member's sign-in date and the length of their contract and returns a modified dataframe with an expiration date for each member. The function works as intended, but I wanted to know if there was a cleaner way of writing the nested function <code>month_to_num(ind)</code>. I know python does not implement <code>cases</code>, but is there a way to rewrite the all the <code>if/elif/else</code> statements? </p>

<pre><code>def renewal_date(df):

    def month_to_num(ind):
        if (df.loc[ind, "Contract Type"] == "1 Month"):
            return 1
        elif (df.loc[ind, "Contract Type"] == "3 Months Prom" or 
              df.loc[ind, "Contract Type"] == "3 Month"):
            return 3
        elif (df.loc[ind, "Contract Type"] == "4 Month Promo"):
            return 4
        elif (df.loc[ind, "Contract Type"] == "6 Months"):
            return 6
        else:
            return 12

    for z in range(0, len(df)): 
        exp_date = (df.loc[z, "Date-Joined"] + 
                    relativedelta(months=+month_to_num(z)))
        df.set_value(z,"Date-Renewal", exp_date)

    return df
</code></pre>