Use a for-loop to create a new DataFrame in Python?

Question

I am working on the Cars.csv DataFrame which can be found here: https://www.kaggle.com/ljanjughazyan/cars1

My goal is to create a new Data Frame with the column names: USA, Europe and Japan and to save the number of cars that are in each category.

for a in list(cars.origin.unique()):
    x= pd.DataFrame({a:[cars.loc[cars["origin"]==a,"origin"].size]})

I tried it with this code, but as a result I obtain a Data Frame with only one column that is "Europe". So it kind of works, but I cant figure why it just dismisses the other values. Why doesnt it work and can it be done using a for-loop?

Thanks in advance!!

Don Fruendo · Accepted Answer · 2021-09-06 10:40:11Z

2

I assume "Europe" would be the last item in your list. Because you are resetting x in every iteration of your for-loop.

So if you print(x) inside the loop, you should first see a DataFrame with just USA, then just Japan and then just Europe, which is your final result.

I would suggest putting the data into a python dict and creating you DataFrame afterwards.

data = {}
for a in list(cars.origin.unique()):
    data[a] = [cars.loc[cars["origin"]==a,"origin"].size]
x = pd.DataFrame(data)

answered Sep 6, 2021 at 10:40

Don Fruendo

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