Merge two columns into one (with NaN values)

Question

I have my table that looks like this:

column A	column B
A
B
C
	D
	E
F
	G

I want it to look like this:

column C
A
B
C
D
E
F
G

Does this answer your question? [How to remove nan value while combining two column in Panda Data frame?](https://stackoverflow.com/questions/34989341/how-to-remove-nan-value-while-combining-two-column-in-panda-data-frame) — Mateen Ulhaq, Mar 18 '22 at 07:47

score 2 · Answer 1 · answered Mar 18 '22 at 07:52

2

A column is major

df['column C'] = df['column A'].fillna(df['column B'])

answered Mar 18 '22 at 07:52

smart lph

131
3

score 1 · Answer 2 · answered Mar 18 '22 at 07:49

If you use pandas, you can bfill and get the first column:

df['column C'] = df[['column A', 'column B']].bfill(1).iloc[:,0]

output:

  column A column B column C
0        A      NaN        A
1        B      NaN        B
2        C      NaN        C
3      NaN        D        D
4      NaN        E        E
5        F      NaN        F
6      NaN        G        G

score 0 · Answer 3 · answered Mar 18 '22 at 07:53

Not sure if that exactly what you want or its just a example but you could do something like this

This is coding from first principles

Column_A = ['A', "B",'C','','','F','']
Column_B = ['', "",'','D','E','','G']
Column_C = ['', "",'','','','','']

print('column C')

for i in range(len(Column_C)):
    if (Column_A[i] !='') :
        Column_C[i] = Column_A[i]
        print(Column_C[i])
    elif (Column_B[i] !='') :
        Column_C[i] = Column_B[i]
        print(Column_C[i])

Merge two columns into one (with NaN values)

3 Answers3