如何复制 dataframe1 中的行数以匹配 pandas 中 dataframe 2 中的 n 行

Question

I just started learning Python a few months ago and just started using StackOverflow as well, please bear with me:
We have the two data frames:

df1:

    0.1,0.2,0.3,0.4  
    1.0,2.0,3.0,4.0
    6.0,7.0,8.0,9.0 

df2:

    Sequence, dataset_ID  
    1,1  
    2,4  
    10,5

I am using python iterrows function to transpose df1 into:

for ind,row in df1.iterrows():
    row.to_csv(path+'\df1Transposed')

df1Transposed:

    0.1,1.0
    0.2,2.0  
    0.3,3.0  
    0.4,4.0
    0.1,6.0
    0.2,7.0  
    0.3,8.0  
    0.4,9.0

I am trying to find a good way to group/replicate each row in df2 to match the number of rows in df1 transposed. For example, 1 transposed header and row in df 1 creates 4 rows and two columns in df1Transposed (0.1-0.4) and repeats again for the next row in df1. So the first row in df2 should repeat 4 times and then the second row should repeat another 4 times.

dfout:

Sequence, dataset_ID,V,I
1,1,0.1,1.0
1,1,0.2,2.0  
1,1,0.3,3.0  
1,1,0.4,4.0  
2,4,0.1,6.0  
2,4,0.2,7.0  
2,4,0.3,8.0  
2,4,0.4,9.0  

Answer 1

You can use a combination of numpy's repeat and arange to get the index, then concatenate the two dataframes horizontally.

First, get the transpose thanks to @sammywemmy handy one-liner:

df1_T = pd.concat([df1.iloc[:2].T,
                   df1.iloc[::2].T.set_axis([0,1],axis=1)],ignore_index=True)

Second get the length of the transpose dataframe, select the number of rows you want to include from df2 and use the functions mentioned above:

df_1_l = df1_T.shape[0]
no_rows_from_df2 = 2
index = np.repeat(np.arange(no_rows_from_df2), df_1_l//rows_df2)

df3 = pd.concat([df1_T.reset_index(drop=True),
             df2.iloc[index].reset_index(drop=True)], axis=1)
df3

#     0 1   Sequence  dataset_ID
# 0 0.1 1.0   1       1
# 1 0.2 2.0   1       1
# 2 0.3 3.0   1       1
# 3 0.4 4.0   1       1
# 4 0.1 6.0   2       4
# 5 0.2 7.0   2       4
# 6 0.3 8.0   2       4
# 7 0.4 9.0   2       4

Few things, this works because the length of df1_T is a mutiple of the selected number of rows in df2, if for example you would like to repeat rows 0,1,2 then the length of df1 should be 3, 6, 9, 12...