[Python] Simplify Code for Grouping, Filtering, and Pie Chart of Game Publisher Sales

I'm currently learning how to use pandas, and I feel like my code could be simplified or made more efficient. I use this data:https://www.kaggle.com/datasets/gregorut/videogamesales

Pb_Sales = df.groupby('Publisher')[['Global_Sales']].sum().sort_values('Global_Sales',ascending=False)
total = Pb_Sales['Global_Sales'].sum()
Pb_Sales['Proportion']=Pb_Sales['Global_Sales']/total
index_position = 0
threshold = 0.02
index_list = list(Pb_Sales.index)
for num in Pb_Sales['Proportion']:
if num < threshold:
index_list[index_position]= 'Other'
index_position=index_position+1
Pb_Sales.index = index_list

Pb_Sales = Pb_Sales.groupby(Pb_Sales.index).sum().sort_values('Global_Sales',ascending = False)
plt.title("most profitable publisehr")
plt.ylabel("")
chart_Pie= Pb_Sales['Global_Sales'].plot(kind = 'pie',figsize=(10,5),legend = False)
chart_Pie.set_ylabel("")
plt.show()


Also,I followed a tutorial to write this code below , but I later read online that it's not recommended to use it — though I'm not sure why.

df['Year'] = df['Year'].astype(int) #I want to make the Year column value to be int not float

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