Imagine we create a pandas series using the below code. What is one simple way to retrieve the value $0\mathrm{.}5$ from the series?

import pandas as pd

$df=pd.$ Series $,$

df

index $($:$={[}^{\text{'}}{a}^{\text{'}},{?}^{\text{'}}{b}^{\text{'}},{?}^{\text{'}}{c}^{\text{'}},{?}^{\text{'}}{d}^{\text{'}}]\}$

$\text{'}$c$\text{'}]$

df$[\text{'}$a$\text{'}]$

$df{[}^{\text{'}}{b}^{\text{'}}]$

df$.$find$[\mathrm{.}50]$

df$[\text{'}$loc$\text{'}]$

df$[\text{'}$d$\text{'}]$

$]=[\mathrm{.}5$