Is there a ONE-LINER way to give each row of a dataframe a unique id consisting of an integer and string?

This is my DataFrame:

import pandas as pd
df = pd.DataFrame(
    {
        'a': [4, 3, 2, 2, 6]
    }
)

And this is the expected output: I want to create column id:

   a   id
0  4  x_0
1  3  x_1
2  2  x_2
3  2  x_3
4  6  x_4

I can create id like this but I think there is a one-liner for this:

df['id'] = np.arange(len(df))
df['id'] = 'x_' + df.id.astype(str)

I prefer a solution that does not use index.

>Solution :

If you want a one-liner, you have to convert your array to Series (raw arrays are not practical for string concatenation):

df['id'] = 'x_' + pd.Series(np.arange(len(df)), dtype=str)

# or
df['id'] = pd.Series(np.arange(len(df)), dtype=str).radd('x_')

Output:

   a   id
0  4  x_0
1  3  x_1
2  2  x_2
3  2  x_3
4  6  x_4