Concatenating two lists

python concatenate multiple lists
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I have a list of lists that looks as follows (I hope I'm right when I said list of lists):

['[175', '178', '182', '172', '167', '164]', "['b']"]

How can I concatenate the two lists? That is, having a list that looks as follows:

[175, 178, 182, 172, 167, 164, b]

Any thoughts?


First, note that that's not a list of lists, but just a list of strings that, when concatenated, might look like one or more (nested) lists, in particular with those [ and ] in the first and last element. Thus, you could join those strings with , to a string that actually represents a pair or tuple of lists, and then eval or ast.literal_eval those. Then just use a list comprehension to flatten that actual list of lists.

>>> lst = ['[175', '178', '182', '172', '167', '164]', "['b']"]

>>> ','.join(lst)

>>> ast.literal_eval(','.join(lst))
([175, 178, 182, 172, 167, 164], ['b'])

>>> [x for sub in ast.literal_eval(','.join(lst)) for x in sub]
[175, 178, 182, 172, 167, 164, 'b']

Python, In this method, we traverse the second list and keep appending elements in the first list, so that first list would have all the elements in both lists and hence would​  The simplest method is just to use the + operator, which returns the concatenation of the lists: concat = first_list + second_list. One disadvantage of this method is that twice the memory is now being used . For very large lists, depending on how you're going to use it once it's created, itertools.chain might be your best bet:

list concatenations work with a + so ...

lsts = ['[175', '178', '182', '172', '167', '164]', "['b']"]
new_lsts = []
for i in lsts:
  new_lsts += i

Also this similar question has been asked here many times.


and here

and probably several other times

Python Join Two Lists, There are several ways to join, or concatenate, two or more lists in Python. One of the easiest ways are by using the + operator. Example. Join two list: list1 =  Lists in Python can be concatenated in two ways. Using + operator. Using extend. Let list_a and list_b be defined as below. list_a = [1, 2, 3, 4] list_b = [5, 6, 7, 8] Using + operator to concatenate two list_a and list_b. list_c = list_a + lis_b. print list_c # Output: [1, 2, 3, 4, 5, 6, 7, 8]

In python you can use + to concat them:

a = [2,5,6]
b = [6,1,4]
c = a+b

How can I get the concatenation of two lists in Python without , Yes: list1 + list2 . This gives a new list that is the concatenation of list1 and list2 . Algorithm for concatenation Let us assume that the two linked lists are referenced by head1 and head2 respectively. 1. If the first linked list is empty then return head2. 2. If the second linked list is empty then return head1. 3. Store the address of the starting node of the first linked list in a… Read More »

How to concatenate Lists In Python?, For example, if we have a list with elements [1, 2, 3] and another list with elements [4, 5, 6] . If we concatenate both the lists, then, the result may  The numbers in the table specify the first browser version that fully supports the method. Method. concat () 1.0. 5.5. 1.0. Yes.

Python Add Lists / Join / Concatenate Two or More Lists, It describes various ways to join/concatenate/add lists in Python. For example – simply appending elements of one list to the tail of the other in a for loop, or using​  In this article, several methods to concatenate multiple lists in Java into a single list are discussed using plain Java, Java 8, Guava Library and Apache Commons Collections. 1. List.addAll() List.addAll(Collection) method concatenates all elements of the specified collection to the end of the list. We can use it inside a for-each loop to concatenate multiple lists as shown below:

Python program to merge / concatenate two lists, In this post, we will see how to concatenate two lists in Python using + operator, operator.add(), itertools.chain(), iterable unpacking operator & extend() There are two methods by which you combine elements of two list variables. The first is the plus(+) operator and the second is the extend in Python. Let’s start describing each method one by one. Using Plus(+) Operator to Concatenate Two List Variables in Python. If you want to concatenate two list variables, you have to use the plus(+). You have to use the below-given example to combine or join the two list elements. It stores the combined list elements to the third variable.