Iterate over list of tuples

Question

I would really appreciate some input on my question - can't seem to make it work. I need to iterate over a list of tuples such as:

li = [('a',1),('b',2),('c', 2),('d', 2), ('e', 3), ('f', 3), ('g', 1)]

and would like to get a result such as:

new_li = [('a', 1), ('bcd',2), ('ef',3), ('g',1)]

where I concatenate strings based on the second value in the tuple. I do not want to use groupby from itertools because even though g is associated with 1, it is not immediately next to a. Thank you for all of the responses!

Answer 1

IIUC, you can use itertools.groupby as it groups sequentially:

For example:

from itertools import groupby
new_li = [
    ("".join(y[0] for y in g), x) for x, g in groupby(li, key=lambda x: x[1])
]
print(new_li)
#[('a', 1), ('bcd', 2), ('ef', 3), ('g', 1)]

The keyfunc for the groupby gets the number from each tuple. Then for each group, you can join the letters together using str.join.