CODEWITHSUNDEEP
pandaslistdataframe
GDog
GDog

Reputation: 165

Dataframe within a Dataframe - to create new column_

For the following dataframe:

import pandas as pd

df=pd.DataFrame({'list_A':[3,3,3,3,3,\
2,2,2,2,2,2,2,4,4,4,4,4,4,4,4,4,4,4,4]})

How can 'list_A' be manipulated to give 'list_B'?

Desired output:

list_A list_B
0 3 1
1 3 1
2 3 1
3 3 0
4 2 1
5 2 1
6 2 0
7 2 0
8 4 1
9 4 1
10 4 1
11 4 1
12 4 0
13 4 0
14 4 0
15 4 0
16 4 0

As you can see, if List_A has the number 3 - then the first 3 values of List_B are '1' and then the value of List_B changes to '0', until List_A changes value again.

Upvotes: 1

Views: 47

Answers (1)

ansev
ansev

Reputation: 30920

GroupBy.cumcount

df['list_B'] = df['list_A'].gt(df.groupby('list_A').cumcount()).astype(int)
print(df)

Output

    list_A  list_B
0        3       1
1        3       1
2        3       1
3        3       0
4        3       0
5        2       1
6        2       1
7        2       0
8        2       0
9        2       0
10       2       0
11       2       0
12       4       1
13       4       1
14       4       1
15       4       1
16       4       0
17       4       0
18       4       0
19       4       0
20       4       0
21       4       0
22       4       0
23       4       0

EDIT

blocks = df['list_A'].ne(df['list_A'].shift()).cumsum()
df['list_B'] = df['list_A'].gt(df.groupby(blocks).cumcount()).astype(int)

Upvotes: 2

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