Add multiple columns with zero values from a list to a Pandas data frame

Question

Say I have a data frame

id col1 col2
1  1    foo
2  1    bar

And a list of column names

l = ['col3', 'col4', 'col5']

How do I add new columns to the data frame with zero as values?

id col1 col2 col3 col4 col5
1  1    foo     0    0    0
2  1    bar     0    0    0

Answer 1

You could try direct assignment (assuming your dataframe is named df):

for col in l:
    df[col] = 0

Or use the DataFrame's assign method, which is a slightly cleaner way of doing it if l can contain a value, an array or any pandas Series constructor.

# create a dictionary of column names and the value you want
d = dict.fromkeys(l, 0)
df.assign(**d)

Pandas Documentation on the assign method : http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.assign.html