如何使熊猫 groupby().count() 求和而不是行？

Question

I am aware that size() is the one that count rows, and count() should be counting values. However, that isn't happening. When I compare the .count() vs .size(), I get the same result, when they should be greatly different. My code:

import pandas as pd

df = pd.read_csv("TEST1.csv",sep=';')

df.columns = ['Time','Type','Value','Size','Buyer']

df['Value'] = pd.to_numeric(df['Value'])
df['Size'] = pd.to_numeric(df['Size'])

n_of_buyers = df.groupby("Buyer")["Size"].count()
print(n_of_buyers)

I thought that by having the df['Size'] = pd.to_numeric(df['Size']) I shouldn't have this issue, and yet...

Thanks ever so much.

Answer 1

我认为您要使用的是GroupBy.sum