Merge dataframes without header

Question

I have foll. dataframes (df_A and df_B):

df_A
Col_A     Col_B
23         34
12         18

df_B
23          12
45          10

I want to merge them based on Col_A in df_A and 1st column in df_B. Note that df_B does not have any header row. How do I do this? A simple merge would have been:

df_A.merge(df_B, on='Col_A')

However that does not work in this case becuase df_B does not have Col_A as column.

--EDIT based on @EdChum's suggestion:

TO CLARIFY: I want to merge two dataframes. One has a header, and the other one does not. How do i specify the join column on a dataframe that does not have a header? Can I specify it by location/index?

df_B.info()
<class 'pandas.core.frame.DataFrame'>
Int64Index: 1 entries, 0 to 0
Data columns (total 2 columns):
23    1 non-null int64
12    1 non-null int64
dtypes: int64(2)
memory usage: 24.0 bytes

df_B.columns.tolist()
['23', '12']


df_A.info()
<class 'pandas.core.frame.DataFrame'>
Int64Index: 2 entries, 0 to 1
Data columns (total 2 columns):
Col_A    2 non-null int64
Col_B    2 non-null int64
dtypes: int64(2)
memory usage: 48.0 bytes

df_A.columns.tolist()
['Col_A', 'Col_B']

Post the output from df_A.info() and df_B.info() and also the output from df_A.columns.tolist() and the same for df_B they will have columns despite what you think — EdChum
– EdChum, Commented Nov 10, 2015 at 15:09
Well it looks like you want to merge like so: df_A.merge(df_B, left_on='Col_A', right_on='23') — EdChum
– EdChum, Commented Nov 10, 2015 at 15:15
Not according to df_B.info(), what does df_B.columns.tolist() show — EdChum
– EdChum, Commented Nov 10, 2015 at 15:17
Well you've answered my question then, you've either imported the file incorrectly or you'll have to merge using my code — EdChum
– EdChum, Commented Nov 10, 2015 at 15:19

jezrael · Accepted Answer · 2015-11-10 15:25:45Z

1

You can set column names by df_B.columns = ['Col_B', 'Col_A']. Then you can merge dataframes.

print df_A
   Col_A  Col_B
0     23     34
1     12     18

print df_B
    0   1
0  23  12
1  45  10

df_B.columns = ['Col_A', 'Col_B']
print df_B
   Col_A  Col_B
0     23     12
1     45     10

out = df_A.merge(df_B, on='Col_A')
print out
   Col_A  Col_B_x  Col_B_y
0     23       34       12

answered Nov 10, 2015 at 15:25

jezrael

868k103 gold badges1.4k silver badges1.3k bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Merge dataframes without header

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related