如果值等于第二个列表元素，则使用第一个列表的元素创建新列

Question

I have a dataset df1 with two columns:

d1=[9,9,26,28,43,43,43,44,85]
df1 = pd.DataFrame(data = d1)
df1['sl']=""

And 2 lists with the same length (but not the same length than the df1):

list1=[9,26,28,43,44,85]
list2=[2,1,1,1,1,1,1]

I would like to add in my column 'sl' (df1), the values of the list2 if the value of my column 1 (of df1) is equal to the elements of the list1.

I mean, expected output for df1:

0 sl
9 2
9 2
26 1
28 1
43 1
43 1
43 1
43 1
44 1
85 1

I have tried a lot of solution before posting but without success...

Thanks a lot,

AL

Answer 1

Use Series.map by dictionary created by zip by both lists:

d1=[9,9,26,28,43,43,43,44,85]
df1 = pd.DataFrame(data = d1)

list1=[9,26,28,43,44,85]
list2=[2,1,1,1,1,1]

df1['sl']= df1[0].map(dict(zip(list1, list2)))
print (df1)
    0  sl
0   9   2
1   9   2
2  26   1
3  28   1
4  43   1
5  43   1
6  43   1
7  44   1
8  85   1