Python code is below.
from itertools import groupby
data = [('a', 1), ('b', 2), ('b', 3), ('c', 4), ('c', 5)]
_sorted_data = sorted(data,key= lambda element : element[0])
_res = groupby(_sorted_data,key=lambda x : x[0])
for key,value in _res:
print(key,list(value))
Got below result.
a [('a', 1)]
b [('b', 2), ('b', 3)]
c [('c', 4), ('c', 5)]
my expected result is
a [1]
b [2,3]
c [4,5]
How can transform the 'Values'
It looks like your actual input is unsorted since you're calling sorted first in your code, resulting in an overall time complexity of O(n log n) despite a linear time complexity when performing itertools.groupby.
You can instead iterate over the input list and aggregate the items in a dict for an overall linear time complexity:
data = [('a', 1), ('b', 2), ('b', 3), ('c', 4), ('c', 5)]
result = {}
for key, value in data:
result.setdefault(key, []).append(value)
for key, values in result.items():
print(key, values)
This outputs:
a [1]
b [2, 3]
c [4, 5]