Python:Query on Conditional Loops and the setdefault method

[sudipb]

>>>listoflists = [['a', 'first'], ['b', 'second'], ['a', 'next'], ['c', 'third'], ['b', 'last']]
>>> dd = {}
>>>for item in listoflists:
... dd.setdefault(item[0], []).append(item)

- The part which mentions 'item[0]' would be to have the first letter of each item in the list we created right ?
- what does the ' [ ] ' signify in this case ? Does it mean to have a null value for each key that we create for the dictionary and add/create the value associated with the key from the append method ?

Regards,
Sudip Bhattacharya

[Motoma]

You are correct, in this case, item[0] represents 'a', 'b', or 'c'.

[] signifies an empty list. If you look at the documentation for setdefault, it will return a the value of the dictionary element specified in the first argument, or, if it has no value, it will return the second argument.