Fill Nan With All The Information From Previous Week

I have a dataframe that looks like: Week Store End Cap UPC 0 1 1 A 123456.0 1 1 1 B 789456.0 2 1 1 B 546879.0 3 1

Solution 1:

Lets try self merge after assigning +1 to week

out = df.merge(df.assign(Week=df['Week'].add(1)),
on=['Week','Store','End Cap'],how='left',suffixes=('','_y'))

out['UPC'] = out['UPC'].fillna(out['UPC_y'])
out = out.loc[:, df.columns]

---

print(out)

    Week  Store End Cap       UPC
0      1      1       A  123456.0
1      1      1       B  789456.0
2      1      1       B  546879.0
3      1      1       C  423156.0
4      1      2       A  231567.0
5      1      2       B  456123.0
6      1      2       D  689741.0
7      2      1       A  321654.0
8      2      1       B  789456.0
9      2      1       B  546879.0
10     2      1       C  852634.0