list - Python: how to find duplicates and sum their values?

Question

[('Visa', 980.5), ('Rogers', 61.5), ('Visa', 215.0)]

for example, I have the list of tuples above, how can i find the duplicates(i.e 'Visa') and sum their values (i.e 980.5+215.0)? The output should be:

[('Visa', 1195.5), ('Rogers', 61.5)]

Answer 1

Use a dictionary:

>>> data = [('Visa', 980.5), ('Rogers', 61.5), ('Visa', 215.0)]
>>> result = {}
>>> for card, value in data:
        total = result.get(card, 0) + value
        result[card] = total

    
>>> print result.items()
[('Visa': 1195.5), ('Rogers': 61.5)]