concatenating list of tuples python-CodePudding

I have a list of tuples as seen below :

l = [(1,'Nick'),(4,'George'),(4,'George'),(3,'Nick')]

what i would like to do is merge the tuples with the same Name and add the corresponding numbers. Result here should be :

l_res = [(4,'Nick'),(8,'George')]

How could this be done using python?

CodePudding user response：

You can use a combination of set and list comprehensions like this:

>>> l = [(1,'Nick'),(4,'George'),(4,'George'),(3,'Nick')]
>>> unique = set(e[1] for e in l)
>>> [(sum([x[0] for x in l if x[1] == n]), n) for n in unique]
[(8, 'George'), (4, 'Nick')]

CodePudding user response：

You can use an intermediate set as suggested in a previous answer or with an intermediate dictionary like this:

l = [(1,'Nick'),(4,'George'),(4,'George'),(3,'Nick')]

d = dict()

for v, t in l:
    d[t] = d.get(t, 0)   v

result = [(v, k) for k, v in d.items()]

print(result)

Output:

[(4, 'Nick'), (8, 'George')]

CodePudding user response：

Probably the cleanest way is by using a Counter dictionary.

from collections import Counter

l = [(1,'Nick'),(4,'George'),(4,'George'),(3,'Nick')]

sum_dict = Counter()
for el in l:
    sum_dict[el[1]]  = el[0]

print(sum_dict) # Output: Counter({'George': 8, 'Nick': 4})

If you really want a list of tuples (which doesn't seem like the best datatype for this data), you can easily convert it with list comprehension over dict.items()

sum_list = [(v,k) for k,v in sum_dict.items()]

print(sum_list) # Output: [('Nick', 4), ('George', 8)]

CodePudding user response：

You want to turn l_res into a dict by name, adding the numbers:

dic = {}
for tup in l:
    num, name = tup
    if name in dic:
        dic[name]  = num
    else:
        dic[name] = num

to turn it back into a list:

l_res = [(dic[k], k) for k in dic]