Boolean for unique value in a column

Question

For my dataframe, e.g.

df = pd.DataFrame([1, 3, 7, 1], columns=[\'data\'])

I want to know for each index if the value is unique in the col

Answer 1

from collections import Counter

c = Counter(df.client.to_list())

df["new_col"] = df.client.apply(lambda x:not(c[x] >1) )