Multiple columns with the same name in Pandas

Question

I am creating a dataframe from a CSV file. I have gone through the docs, multiple SO posts, links as I have just started Pandas but didn't get it. The CSV file has multiple columns with same names say a.

So after forming dataframe and when I do df['a'] which value will it return? It does not return all values.

Also only one of the values will have a string rest will be None. How can I get that column?

Answer 1

the relevant parameter is mangle_dupe_cols

from the docs

mangle_dupe_cols : boolean, default True
    Duplicate columns will be specified as 'X.0'...'X.N', rather than 'X'...'X'

by default, all of your 'a' columns get named 'a.0'...'a.N' as specified above.

if you used mangle_dupe_cols=False, importing this csv would produce an error.

you can get all of your columns with

df.filter(like='a')

---

demonstration

from StringIO import StringIO
import pandas as pd

txt = """a, a, a, b, c, d
1, 2, 3, 4, 5, 6
7, 8, 9, 10, 11, 12"""

df = pd.read_csv(StringIO(txt), skipinitialspace=True)
df

df.filter(like='a')