Keep all row with interval of 3 in python

Question

I have a dataframe such as :

COL1 COL2 COL3 
A    B    C
D    E    F
G    G    I
J    K    L
M    N    O
P    Q    R
S    T    U
V    W    X
Y    Z    A

and I would like to keep only intervals of 3 rows. I should then get :

COL1 COL2 COL3 
G    G    I
P    Q    R
Y    Z    A

Does someone have an idea?

Does this answer your question? [Pandas every nth row](https://stackoverflow.com/questions/25055712/pandas-every-nth-row) — Mykola Zotko, Nov 30 '21 at 16:22

score 4 · Accepted Answer · answered Nov 30 '21 at 15:57

4

You can use .iloc and range:

df.iloc[range(2,len(df),3)]

answered Nov 30 '21 at 15:57

Youssef_boughanmi

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score 4 · Answer 2 · answered Nov 30 '21 at 16:03

4

Wouldn't a slicing do the job?:

df[2::3]

answered Nov 30 '21 at 16:03

nikeros

3,302
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score 4 · Answer 3 · answered Nov 30 '21 at 16:09

4

The iloc property allows you to access slices of a dataframe similarly to a 2d numpy array, of a 1d list/tuple if slicing along the index (first axis).

In your case, as @QuangHoang answered:

df.iloc[2::3]

answered Nov 30 '21 at 16:09

Learning is a mess

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score 2 · Answer 4 · answered Nov 30 '21 at 16:16

2

Try groupby

out = df.groupby(df.index//3).tail(1)
Out[446]: 
  COL1 COL2 COL3
2    G    G    I
5    P    Q    R
8    Y    Z    A

answered Nov 30 '21 at 16:16

BENY

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Keep all row with interval of 3 in python

4 Answers4