How do I use groupby in Python's itertools?

Can you explain how to use the groupby function from itertools in Python?

Sure! The groupby function in itertools groups adjacent elements in an iterable that have the same value. You need to sort the data first if you want to group non-adjacent duplicates.

Can you provide a code example?

Absolutely! Here's a simple example:

from itertools import groupby

data = [('a', 1), ('a', 2), ('b', 1), ('b', 2)]

# Sort the data by the first element
data.sort(key=lambda x: x[0])

# Group by the first element
for key, group in groupby(data, key=lambda x: x[0]):
    print(key, list(group))

This will output:

a [(‘a’, 1), (‘a’, 2)]
b [(‘b’, 1), (‘b’, 2)]

What if I want to group by a specific attribute in a list of dictionaries?

You can use a similar approach! Just specify the key function to extract the attribute you want to group by. For example:

from itertools import groupby

data = [{'name': 'Alice', 'age': 30}, {'name': 'Bob', 'age': 30}, {'name': 'Charlie', 'age': 25}]

data.sort(key=lambda x: x['age'])

for key, group in groupby(data, key=lambda x: x['age']):
    print(key, list(group))