concatenate pairs of consecutive sublists in a list using python

You could use zip_longest with a fill value (in case your list has an odd number of sublists) to zip an iterator over list1. Running a list comprehension over the zip generator object allows you to concatenate the consecutive pairs of lists:

>>> from itertools
import zip_longest # izip_longest in Python 2. x >>>
   x = iter(list1) >>>
   [a + b
      for a, b in zip_longest(x, x, fillvalue = [])
   ]
   [
      [1, 2, 3, 4, 5],
      [6, 7, 8],
      [9, 10]
   ]

Try using a list comprehension (but be careful with the indexes!). It works for lists with an even or odd number of sublists:

list1 = [
   [1, 2, 3],
   [4, 5],
   [6],
   [7, 8],
   [9, 10]
]
n = len(list1)

[list1[i] + (list1[i + 1]
   if i + 1 < n
   else []) for i in xrange(0, n, 2)] => [
   [1, 2, 3, 4, 5],
   [6, 7, 8],
   [9, 10]
]

list1 = [
   [1, 2, 3],
   [4, 5],
   [6],
   [7, 8],
   [9, 10]
]

length = len(list1)
new_list = [list1[i] + list1[i + 1]
   if i + 1 < length
   else [list1[i]]
   for i in range(0, length, 2)
]

print(new_list)

1._

>>> list1 = [
      [1, 2, 3],
      [4, 5],
      [6],
      [7, 8],
      [9, 10]
   ] >>>
   list1[[1, 2, 3], [4, 5], [6], [7, 8], [9, 10]]

Now we can do:

>>> test = [list1[0] + list1[1]] + [list1[2] + list1[3]] + list1[4] >>>
   test[[1, 2, 3, 4, 5], [6, 7, 8], 9, 10] >>>

1._

list1 = [
   [1, 2, 3],
   [4, 5],
   [6],
   [7, 8],
   [9, 10]
]
from itertools
import islice, chain

print([list(chain.from_iterable(islice(list1, i, i + 2)))
   for i in range(0, len(list1), 2)
])[[1, 2, 3, 4, 5], [6, 7, 8], [9, 10]]

Or without islice:

print([list(chain.from_iterable(list1[i: i + 2]))
   for i in range(0, len(list1), 2)
])[[1, 2, 3, 4, 5], [6, 7, 8], [9, 10]]

Use a simple loop:

list1 = [
   [1, 2, 3],
   [4, 5],
   [6],
   [7, 8],
   [9, 10]
]

newlist = []

for i in range(0, len(list1), 2):
   newlist.append(list1[i] + list1[i + 1])
if len(list1) % 2 > 0:
   newlist.append(list1[-1])

print newlist

Suggestion : 2

Last Updated : 18 May, 2020

    The original list: [5, 4, 1, 3, 2]
    The consecutive element paired list is: [
       [5, 4],
       [4, 1],
       [1, 3],
       [3, 2]
    ]

Suggestion : 3

A list is an ordered set of values, where each value is identified by an index. The values that make up a list are called its elements. Lists are similar to strings, which are ordered sets of characters, except that the elements of a list can have any type. Lists and strings — and other things that behave like ordered sets — are called sequences.,Functions which take lists as arguments and change them during execution are called modifiers and the changes they make are called side effects.,There are several ways to create a new list; the simplest is to enclose the elements in square brackets ( [ and ]):,If there is a third argument, it specifies the space between successive values, which is called the step size. This example counts from 1 to 10 by steps of 2:

[10, 20, 30, 40]
["spam", "bungee", "swallow"]

["hello", 2.0, 5, [10, 20]]

>>>
if []:
...print 'This is true.'
   ...
   else:
      ...print 'This is false.'
      ...
      This is false. >>>

>>> vocabulary = ["ameliorate", "castigate", "defenestrate"] >>>
   numbers = [17, 123] >>>
   empty = [] >>>
   print vocabulary, numbers, empty['ameliorate', 'castigate', 'defenestrate'][17, 123][]

>>> print numbers[0]
17

>>> numbers[9-8]
123
>>> numbers[1.0]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
      TypeError: list indices must be integers

Suggestion : 4

If we output the element at index 3, we get:,We can also remove elements from a list by assigning an empty list to them:,After we execute these assignment statements,If you try to access or assign to an element that does not exist, you get a runtime error:

1
2

ps = [10, 20, 30, 40]
qs = ["spam", "bungee", "swallow"]

zs = ["hello", 2.0, 5, [10, 20]]

>>> vocabulary = ["apple", "cheese", "dog"] >>>
   numbers = [17, 123] >>>
   an_empty_list = [] >>>
   print(vocabulary, numbers, an_empty_list)["apple", "cheese", "dog"][17, 123][]