我怎么能在另一个 df 行下 append pandas dataframe 行

Question

I have 2 pandas dataframe, one df has the id column and another df has values i want to add df1.

df1:

id	Column A	Column B
1	red	rose
2	blue	rose
3	yellow	rose

df2

id	Column A	Column B
null	green	car
null	grey	car

i want to append df2 values to df1 but i need to append data for all id numbers.

output i am trying to get:

id	Column A	Column B
1	red	rose
1	green	car
1	grey	car
2	blue	rose
2	green	car
2	grey	car
3	yellow	rose
3	green	car
3	grey	car

i tried with the for and if else statements but im stuck it

Answer 1

You can try cross appling ids from the first dataframe with second one and the concatenating the results:

data = [[1,'red',   'rose'], [2,'blue', 'rose'], [3,'yellow', 'rose']]
df = pd.DataFrame(data, columns=["id", "Column A", "Column B"])

data1 = [['green', 'car' ],['grey','car']]
df1 = pd.DataFrame(data1, columns=["Column A", "Column B"])


pd.concat([df, df[['id']].merge(df1, how='cross')])

Note that this will contain duplicates if some id from df1 will already have data as one of the rows in df2 .

Output:

id	Column A	Column B
1	red	rose
2	blue	rose
3	yellow	rose
1	green	car
1	grey	car
2	green	car
2	grey	car
3	green	car
3	grey	car