add first column to dataframe pandas code example

Example 1: how to add the column to the beginning of dataframe

# Third position would be at index 2, because of zero-indexing.
df.insert(2, 'new-col', data)

Example 2: add column using a list at poisition zero pandas

df = pd.DataFrame({'B': [1, 2, 3], 'C': [4, 5, 6]})

df
Out: 
   B  C
0  1  4
1  2  5
2  3  6

idx = 0
new_col = [7, 8, 9]  # can be a list, a Series, an array or a scalar   
df.insert(loc=idx, column='A', value=new_col)

df
Out: 
   A  B  C
0  7  1  4
1  8  2  5
2  9  3  6