pandas add columns when read from a csv file

Question

I want to read from a CSV file using pandas read_csv. The CSV file doesn't have column names. When I use pandas to read the CSV file, the first row is set as columns by default. But when I use df.columns = ['ID', 'CODE'], the first row is gone. I want to add, not replace.

df = pd.read_csv(CSV)
df

    a   55000G707270
0   b   5l0000D35270
1   c   5l0000D63630
2   d   5l0000G45630
3   e   5l000G191200
4   f   55000G703240


df.columns=['ID','CODE']
df

    ID          CODE
0   b   5l0000D35270
1   c   5l0000D63630
2   d   5l0000G45630
3   e   5l000G191200
4   f   55000G703240

Possible duplicate of [How to add header row to a pandas DataFrame](http://stackoverflow.com/questions/34091877/how-to-add-header-row-to-a-pandas-dataframe) — Leb, Dec 24 '16 at 13:04

score 10 · Accepted Answer · answered Dec 24 '16 at 10:03

I think you need parameter names in read_csv:

df = pd.read_csv(CSV, names=['ID','CODE'])

names : array-like, default None

List of column names to use. If file contains no header row, then you should explicitly pass header=None. Duplicates in this list are not allowed unless mangle_dupe_cols=True, which is the default.

score 1 · Answer 2 · answered Dec 24 '16 at 10:04

1

You may pass the column names at the time of reading the csv file itself as :

df = pd.read_csv(csv_path, names = ["ID", "CODE"])

answered Dec 24 '16 at 10:04

ZdaR

22,343
7
66
87

score 1 · Answer 3 · answered Dec 24 '16 at 10:04

1

Use names argument in function call to add the columns yourself:

df = pd.read_csv(CSV, names=['ID','CODE'])

answered Dec 24 '16 at 10:04

Carles Mitjans

4,786
3
19
38

score 1 · Answer 4 · answered Dec 24 '16 at 13:00

1

you need both: header=None and names=['ID','CODE'], because there are no column names/labels/headers in your CSV file:

df = pd.read_csv(CSV, header=None, names=['ID','CODE'])

answered Dec 24 '16 at 13:00

MaxU - stand with Ukraine

205,989
36
386
419

score 1 · Answer 5 · answered Jun 04 '20 at 18:01

The reason there are extra index columns add is because to_csv() writes an index per default, so you can either disable index when saving your CSV:

df.to_csv('file.csv', index=False)

or you can specify an index column when reading:

df = pd.read_csv('file.csv', index_col=0)

pandas add columns when read from a csv file

5 Answers5