How to elaborate my program by using an account name appended with an integer to distinguish different account names?

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Python

Here's my question, For the account name above, if an account name already exists, use an account name appended with an integer to distinguish different account names. For example, if there are three patients with the same account name “abranch”, the second one should be named as “abranch1” and the third one should be named as “abranch2”. How to elaborate my program by using an account name appended with an integer to distinguish different account names?

Here's are my template of the name list：

I would be most appreciate if you help me!

What I have tried:

with open('all_patients.txt', 'r') as fh:
    for line in fh:

        splited_list = line.split()
        surname = splited_list[1]
        given_name = splited_list[0][0]
        patient_name_u = given_name + surname
        patient_name.append(patient_name_u.lower())

fh.close()
print(patient_name)