[python] Pandas 簡易處理資料

主要用於一個大型的 DataFrame 怎麼把其中某個 Column 的值減去某個特定值，雖然直觀但是超好用的！ 一定要記下來XD

import pandas as pd



ds = pd.DataFrame(np.arange(12).reshape(3,4), cols=['A','B','C','Average'])



ds['A'] = ds['A'] - ds['Average']

ds['B'] = ds['B'] - ds['Average']

ds['C'] = ds['C'] - ds['Average']

#Pandas is easy like that!



#Oh, that does it for the entire DF. You only want it for the firs row is that right?



ds.loc[1, 'A'] = ds.loc[1, 'A'] - ds.loc[1, 'Average']

ds.loc[1, 'B'] = ds.loc[1, 'B'] - ds.loc[1, 'Average']

ds.loc[1, 'C'] = ds.loc[1, 'C'] - ds.loc[1, 'Average']

#or in a loop:


for col in ['A', 'B', 'C']:

    ds.loc[1, col] = df.loc[1, col] - ds.loc[1, 'Average']



#and so on...



#if you have thousands of columns then simply do:

for col in ds.columns:

    ds[col] = ds[col] - ds['Average']