CODEWITHSUNDEEP
pythonpandasdataframecounting
Jake
Jake

Reputation: 474

Counting every two rows with the same number in Python

I have a dataframe where every two rows are related. I am trying to give every two rows a unique ID. I thought it would be much easier but I cannot figure it out. Let's say I have this dataframe:

df = pd.DataFrame({'Var1': ['A', 2, 'C', 7], 'Var2': ['B', 5, 'D', 9]})
print(df)

Var1 Var2
   A    B
   2    5
   C    D
   7    9

I would like to add an ID that would result in a dataframe that looks like this:

df = pd.DataFrame({'ID' : [1,1,2,2],'Var1': ['A', 2, 'C', 7], 'Var2': ['B', 5, 'D', 9]})
print(df)

ID Var1 Var2
1    A    B
1    2    5
2    C    D
2    7    9

This is just a sample, but every two rows are related so just trying to count by 1, 1, 2, 2, 3, 3 etc in the ID column.

Thanks for any help!

Upvotes: 0

Views: 264

Answers (2)

BushMinusZero
BushMinusZero

Reputation: 1292

I don't think think is a native Pandas way to do it but this works...

import pandas as pd

df = pd.DataFrame({'Var1': ['A', 2, 'C', 7], 'Var2': ['B', 5, 'D', 9]})
df['ID'] = 1 + df.index // 2
df[['ID', 'Var1', 'Var2']]

Output:

   ID Var1 Var2
0   1    A    B
1   1    2    5
2   2    C    D
3   2    7    9

Upvotes: 1

akuiper
akuiper

Reputation: 215057

You can create a sequence first and then divide it by 2 (integer division):

import numpy as np
df['ID'] = np.arange(len(df)) // 2 + 1
df

#  Var1 Var2  ID
#0    A    B   1
#1    2    5   1
#2    C    D   2
#3    7    9   2

Upvotes: 1

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