How to convert the column into one hot encoded column?

Question

I have a column in my DataFrame as shown below:

City

1) London
2) Birmingham
3) Lahore
4) Paris
    .
    .

I want to convert this column into one hot encoded. The output should look like as:

   City

1) [1,0,0,0]
2) [0,1,0,0]
3) [0,0,1,0]
4) [0,0,0,1]

code showing output:

    pd.get_dummies(dff['city (S)'], prefix='city_')

    city__Kingston  city__Liverpool city__London    
    0                   0               0
    0                   0               0
    0                   0               1
    0                   0               0 

I want in a single column only, not separate

Answer 1

Hard to be sure without actually looking at the data but something like this should do the trick:

import pandas as pd

pd.get_dummies(df['City'], prefix='city_')

Answer 2

You could use the OneHotEncoder from sklearn

from sklearn.preprocessing import OneHotEncoder
oe = OneHotEncoder(sparse=False)
df['City'] = oe.fit_transform(df['City'])

sparse=False shows all the 0.