A loop to find min values based on another column value, and merge into 1 dataframe?

Question

Imagine a dataframe like this:

import pandas as pd
list ={'Security ID':['3e09ax', 'we9lkl', 'as42we','as5322', 'ot24tas', 'c34ci46a8'],
          'Industry':['Airplanes', 'Airplanes', 'Oil', 'Oil', 'Housing', 'Trucking'],
          'Amount outstanding':[33, 31, 39, 21, 29, 29]}
df = pd.DataFrame(list)

'''

The end goal is to return rows for each Industry for the lowest (min) Amount Outstanding into a "Min Value" dataframe for a daily report

essentially this but for each industry:

df[df['Amount outstanding'] == df['Amount outstanding'].min()]

First step is get Unique Values for [Industry] into a list again and then generate a loop function that does this.

Not sure exactly how to this. This dataframe in reality is 100,000 rows with 30 industries that change daily.

Answer 1

IIUC, you want groupby and transform :

output = df[df['Amount outstanding']==df.groupby('Industry')['Amount outstanding'].transform(min)]

>>> output

  Security ID   Industry  Amount outstanding
1      we9lkl  Airplanes                  31
3      as5322        Oil                  21
4     ot24tas    Housing                  29
5   c34ci46a8   Trucking                  29

Answer 2

df['B']=df['Amount outstanding'] 
df.groupby('Industry', group_keys=False).apply(lambda x: x.loc[x.B.idxmin()])

this gives you a new dataframe only with min value in column Amount outstanding. If you want you can drop now the column 'B'

Answer 3

df.loc[df.groupby('Industry')['Amount outstanding'].idxmin()]