How to create a new variable that tells us if the value in a given column is unique or not?

I’m working on the titanic dataset and figured that determining if a ticket is unique or not might be predictive. I’ve written some code below that tells us if the value is unique or not but I have a feeling that there is a much cleaner way of doing this.

 import pandas as pd
dummy_data = pd.DataFrame({"Ticket" : ['A','A','B','B','C','D']
                     })

dummy_data
counts = dummy_data['Ticket'].value_counts()
a = counts[counts>1] 
b=a.reset_index(name='Quantity')
b = b.rename(columns={'index': 'Tickets'})
b
dummy_data['Ticket_multiple'] = np.where(dummy_data['Ticket'].isin(b['Tickets']),1,0)
dummy_data.head(10)

>Solution :

You can use pandas.Series.duplicated with keep=False:

Parameters: keep{‘first’, ‘last’, False}, default ‘first’ :
Method to handle dropping duplicates:

• ‘first’ : Mark duplicates as True except for the first occurrence.
• ‘last’ : Mark duplicates as True except for the last occurrence.
• False : Mark all duplicates as True.

dummy_data['Ticket_multiple'] = dummy_data["Ticket"].duplicated(keep=False).astype(int)

​
Output :

print(dummy_data)

  Ticket  Ticket_multiple
0      A                1
1      A                1
2      B                1
3      B                1
4      C                0
5      D                0