Combine/Merge Lists by Elements Names

Combine/merge lists by elements names (list in list)

Inspired by josilber's answer, here we do not hard-code the length of the sublists and use lapply to create them in the result:

keys <- unique(c(names(l.1), names(l.2)))
setNames(lapply(keys, function(key) {
    l1 <- l.1[[key]]
    l2 <- l.2[[key]]
    len <- max(length(l1), length(l2))

    lapply(seq(len), function(i) c(l1[[i]], l2[[i]]))
  }),
  keys)

Combine/merge lists by elements names (list in list in list)

You just need to use lapply two more times with user-defined functions:

keys <- unique(unlist(lapply(l.new, names)))
l2  <- setNames(lapply(keys, function(key) {
  len <- max(unlist(lapply(l.new, function(x) length(x[[key]]))))
  lapply(seq(len), function(i) unlist(lapply(l.new, function(x) x[[key]][[i]])))
}), keys)
all.equal(l, l2)
# [1] TRUE

Combine/merge lists by elements names

You can do:

keys <- unique(c(names(lst1), names(lst2)))
setNames(mapply(c, lst1[keys], lst2[keys]), keys)

---

Generalization to any number of lists would require a mix of do.call and lapply:

l <- list(lst1, lst2, lst1)
keys <- unique(unlist(lapply(l, names)))
setNames(do.call(mapply, c(FUN=c, lapply(l, `[`, keys))), keys)

combine list elements based on element names

sapply(unique(names(L1)), function(x) unname(unlist(L1[names(L1)==x])), simplify=FALSE)
$F01
[1] 1 2 3 4 5 6 7 8 9

$F02
[1] 10 20 30 40 50

How to merge elements of two lists at the same index in Python?

One way to do this is to zip the input lists then add them:

a = [['a', 1], ['b', 2], ['c', 3]]
b = [10, 20, 30]

c = [x+[y] for x, y in zip(a, b)]
print(c)  # -> [['a', 1, 10], ['b', 2, 20], ['c', 3, 30]]

join list of lists in python

import itertools
a = [['a','b'], ['c']]
print(list(itertools.chain.from_iterable(a)))

R merge two lists into one, drawing elements from each list alternatively

Using Map append the corresponding list elements of 's1' and 's2' as a list and then with do.call(c, flatten the nested list to a list of depth 1.

do.call(c, Map(list, s1, s2))

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Or another option is to rbind the list elements into a matrix and remove the dim attributes with c

c(rbind(s1, s2))

Merge lists that share common elements

You can see your list as a notation for a Graph, ie ['a','b','c'] is a graph with 3 nodes connected to each other. The problem you are trying to solve is finding connected components in this graph.

You can use NetworkX for this, which has the advantage that it's pretty much guaranteed to be correct:

l = [['a','b','c'],['b','d','e'],['k'],['o','p'],['e','f'],['p','a'],['d','g']]

import networkx 
from networkx.algorithms.components.connected import connected_components


def to_graph(l):
    G = networkx.Graph()
    for part in l:
        # each sublist is a bunch of nodes
        G.add_nodes_from(part)
        # it also imlies a number of edges:
        G.add_edges_from(to_edges(part))
    return G

def to_edges(l):
    """ 
        treat `l` as a Graph and returns it's edges 
        to_edges(['a','b','c','d']) -> [(a,b), (b,c),(c,d)]
    """
    it = iter(l)
    last = next(it)

    for current in it:
        yield last, current
        last = current    

G = to_graph(l)
print connected_components(G)
# prints [['a', 'c', 'b', 'e', 'd', 'g', 'f', 'o', 'p'], ['k']]

To solve this efficiently yourself you have to convert the list into something graph-ish anyways, so you might as well use networkX from the start.

how can I combine list elements inside list based on element value?

There is a differnet way to do it using groupby function from itertools. Also there are ways to convert your dict to a list also. It totally depends on what you want.

from itertools import groupby

lis = [['steve','reporter','12','34','22','98'],['megan','arch','44','98','32','22'],['jack','doctor','80','32','65','20'],['steve','dancer','66','31','54','12']]

lis.sort(key = lambda x: x[0])
output = []
for name , groups in groupby(lis, key = lambda x: x[0]):
    temp_list = [name]
    for group in groups:
        temp_list.extend(group[1:])
    output.append(temp_list)

print(output)

OUTPUT

[['jack', 'doctor', '80', '32', '65', '20'], ['megan', 'arch', '44', '98', '32', '22'], ['steve', 'reporter', '12', '34', '22', '98', 'dancer', '66', '31', '54', '12']] 

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