Remove if similar values available based on two columns

[klllmmm]

I want to remove the duplicates (keeping only the first occurrence) if similar values are found between two columns.

import pandas as pd
df1 = pd.DataFrame({'Customer':['John Tom', 'Harry', 'Simon', 'Tom'],
                    'Supplier':['Harry', 'John Tom', 'Harry', 'Simon']})

ie. I want to remove the second-row values as both values in that row were found previously in two columns in one row.

My expected result

Output:
   Customer Supplier
0  John Tom    Harry
1     Simon    Harry
2       Tom    Simon

Is there a way to remove such occurrences by considering them as duplicates?

appreciate it if someone can help

[Larz60+]

import pandas as pd

df1 = pd.DataFrame({'Customer':['John Tom', 'Harry', 'Simon', 'Tom'],
    'Supplier':['Harry', 'John Tom', 'Harry', 'Simon']})

for idx in df1:
    eseries = pd.Series(df1[idx])
    print(f"df1[{idx}] unique = {eseries.unique()}")

results:

Output:
df1[Customer] unique = ['John Tom' 'Harry' 'Simon' 'Tom']
df1[Supplier] unique = ['Harry' 'John Tom' 'Simon']