How do I return values of one column (within a value threshold) based on the values of other columns in the same row?

Question

So here is an example of what my dataset would look like below. It would probably be in the form of a pandas dataframe, but can be anything that is accessible in python.

Let's say for example my 'Thing' of interest was 'Egg'. I would like to search through all of the rows of the Thing1 and Thing2 columns for whenever 'Egg' appears in one of these columns, and if the value in the PairScore column in this same same row is below 3, then I would like to return the 'Thing' that occupies the other column.

So for this example, the first 'Thing' that would be returned would be 'Football' from row 9. And then would want to store all of the 'Things' that get returned in something like a list or maybe a new dataframe.

I hope this makes sense, if I need to expand on anything please let me know! :)

Answer 1

prevs = []
data = df[(~df[['Thing1', 'Thing2']].isin(prevs)).all(1)) & (df[['Thing1', 'Thing2']] == 'Egg').any(1) & (df['PairScore'] < 3)]
df = pd.Series(data.values.flatten())
prevs += df.loc[df != "Egg"].tolist() + "Egg"

Answer 2

For two columns, I'd just use a combination of boolean indexes:

data = {'Thing1': ['Egg', 'Apple', 'Dog', 'Cat', 'Banana', 'Man', 'Elephant', 'Football', 'Egg', 'Elephant', 
                   'Rome', 'Pakistan', 'Egg', 'Dog', 'Banana', 'Rome', 'Apple', 'Lime', 'Album'], 
        'Thing2': ['Lemon', 'Birmingham', 'Egg', 'Dog', 'Germany', 'Flower', 'Banana', 'Egg', 'Birmingham', 
                   'School', 'Lake', 'Swimmer', 'Woman', 'Flower', 'Football', 'Egg', 'Waterfall', 'Egg', 'Bat'], 
        'PairScore': [3, 2, 5, 6, 4, 1, 8, 2, 6, 4, 3, 2, 4, 5, 6, 7, 3, 2, 1]}

df = pd.DataFrame(data)

>>> df.head()
   Thing1      Thing2  PairScore
0     Egg       Lemon          3
1   Apple  Birmingham          2
2     Dog         Egg          5
3     Cat         Dog          6
4  Banana     Germany          4

Selecting as per your criteria

m = df.Thing1.eq("Egg") | df.Thing2.eq("Egg")
# or even m = df.filter(like="Thing").eq("Egg").any(axis=1)
df2 = df[m & df.PairScore.lt(3)]

Result:

      Thing1 Thing2  PairScore
7   Football    Egg          2
17      Lime    Egg          2

From there, one option to proceed is to .stack() the Thing columns into a single column, e.g., do df3[~df3.eq("Egg")] to get rid of rows containing "Egg".

>>> df3 = df2.filter(like="Thing").stack()
>>> df3
7   Thing1    Football
    Thing2         Egg
17  Thing1        Lime
    Thing2         Egg
dtype: object
>>> df3[~df3.eq("Egg")]
7   Thing1    Football
17  Thing1        Lime
dtype: object

In order to do subsequent analyses on df, excluding the rows from df2 above, you can proceed with

>>> df4 = pd.concat([df, df2]).drop_duplicates(keep=False)

df4 now contains everything from df except of the previous matches:

>>> df4.tail()
    Thing1     Thing2  PairScore
13     Dog     Flower          5
14  Banana   Football          6
15    Rome        Egg          7
16   Apple  Waterfall          3
18   Album        Bat          1 # 17 is gone