Python Pandas Dataframe Delete Rows by Value from List

Question

I have a rather simple question, but I can't find a clean way to do it. I would like to delete a number of rows from my dataframe, based on their value in a specific column (id), but I only want to delete one occurrence at a time (preferably random). Here is an example:

I have the following list of ids, that I want to delete:

idsToDelete = [1,2,2,3,3]

In other words, I would like to delete one random row with id = 1, two random rows with id 2 and two random rows with id 3.

I have the follwoing dataframe:

list1 = np.array([[1,0],[1,0],[2,0],[2,0],[2,0],[2,0],[3,0],[3,0],[3,0]])
df = pd.DataFrame(list1, columns=["id","class"])

id | class
------ | ------ 
1 | 0
1 | 0
2 | 0
2 | 0
2 | 0
2 | 0
3 | 0
3 | 0
3 | 0

My goal is to get this dataframe:

id | class
------ | ------ 
1 | 0
2 | 0
2 | 0
3 | 0

Any ideas?

No I do not want to delete duplicates, I would like to delete one random row with id 1, 3 random rows with id 2 and 2 random rows with id 3. Hypothetically there could be duplicates in the output. I change the example to make it clearer. — SirTobi
– SirTobi, Commented Aug 25, 2017 at 14:36

SirTobi · Accepted Answer · 2017-08-25 14:55:32Z

1

This works, but it is not random:

for currentID in idsToDelete:
    df = df.drop(df[df.id == currentID].index[0])

answered Aug 25, 2017 at 14:55

SirTobi

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3 Comments

cs95 Over a year ago

And happens to be iterative too. yeesh.

cs95 Over a year ago

You could turn this around - pass a list of ids you want to keep. There is a vectorised solution for that.

user7870824 Over a year ago

you can use the "sample" method to shuffle the dataframe: sample(frac=1)

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