Python append one list to another

Append one List to another List in Python

This article will discuss different ways to append elements of one list to another list in Python.

Table Of Contents

Append one list to another using extend() function

In Python, the list provides a method extend(iterable). It accepts an iterable sequence as an argument and appends all the elements of iterable to the calling list object. Let’s use this to add elements of one list to another, for example,

first = [11, 12, 13, 14, 15, 16] second = [77, 76, 75, 74, 73, 72] # Append elements of list 'second' to the list 'first' first.extend(second) print(first)

[11, 12, 13, 14, 15, 16, 77, 76, 75, 74, 73, 72]

It modified the calling list object “first” by adding all the elements from list “second” to the list “first”.

Frequently Asked:

Append one or more lists using itertools.chain() function

Python provides module itertools, which contain functions to handle iterators. One of the functions in the itertools module is chain(*iterables). It accepts multiple iterables, groups them, and returns a new iterator. If we loop over the returned iterator object, it starts from the items from the first internal iterable. Once it is done with an internal iterable, it proceeds to the next internal iterable until all iterables are done. We can use this to merge two or more lists, for example,

import itertools first = [11, 12, 13, 14, 15, 16] second = [77, 76, 75, 74, 73, 72] third = [91, 92, 93, 94] # Add elements of all the three lists to a new list final_list = list(itertools.chain(first, second, third)) print(final_list)

[11, 12, 13, 14, 15, 16, 77, 76, 75, 74, 73, 72, 91, 92, 93, 94]

We passed three lists to the chain() function and converted the returned iterable to a new list. All the elements of the three lists got added to the new list.

Append one or more lists using + operator

We can also add two or more lists together using the + operator in Python. For example,

first = [11, 12, 13, 14, 15, 16] second = [77, 76, 75, 74, 73, 72] third = [91, 92, 93, 94] # Add elements of all the three lists to a new list final_list = first + second + third print(final_list)

[11, 12, 13, 14, 15, 16, 77, 76, 75, 74, 73, 72, 91, 92, 93, 94]

It is a simple and elegant solution to merge all the lists.

The complete example is as follows

first = [11, 12, 13, 14, 15, 16] second = [77, 76, 75, 74, 73, 72] # Append elements of list 'second' to the list 'first' first.extend(second) print(first) import itertools first = [11, 12, 13, 14, 15, 16] second = [77, 76, 75, 74, 73, 72] third = [91, 92, 93, 94] # Add elements of all the three lists to a new list final_list = list(itertools.chain(first, second, third)) print(final_list) first = [11, 12, 13, 14, 15, 16] second = [77, 76, 75, 74, 73, 72] third = [91, 92, 93, 94] # Add elements of all the three lists to a new list final_list = first + second + third print(final_list)

[11, 12, 13, 14, 15, 16, 77, 76, 75, 74, 73, 72] [11, 12, 13, 14, 15, 16, 77, 76, 75, 74, 73, 72, 91, 92, 93, 94] [11, 12, 13, 14, 15, 16, 77, 76, 75, 74, 73, 72, 91, 92, 93, 94]

We learned different ways to merge two or more lists in Python.

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Python Append List to a List Example

How to append a list to another list in Python? We are often required to append a list to another list to create a nested list. Python provides an append() method to append a list as an element to another list. In case you wanted to append elements from one list to another list, you can either use the extend() or insert() with for loop.

1. Quick Examples of Append List to a List

Following are quick examples of appending a list to another list.

 # Append list into another list languages1.append(languages2) # Append multiple lists into another list languages1.append([languages2,languages3]) # Append list elements to list languages1.extend(languages2) # Append List Elements using insert() for x in languages2: languages1.insert(len(languages1),x) 

2. Append List as an Element into Another List

To append the python list as an element into another list, you can use the append() from the list. This takes either string, number, or iterable as an argument and appends it at the end of the list.

 # Consider two lists languages1=['Python','PHP','Java',] languages2=['C','C++','C#'] print("Language List 1: ",languages1) print("Language List 2: ",languages2) # Append list into another list languages1.append(languages2) print("Result: ",languages1) 

This example yields the below output.

Similarly, you can also append multiple lists to another list.

 # Consider three lists languages1=['Python','PHP','Java',] languages2=['C','C++','C#'] languages3=["Scala","Ruby"] print("Language List 1: ",languages1) print("Language List 2: ",languages2) print("Language List 3: ",languages3) # Append multiple lists into another list languages1.append([languages2,languages3]) print("Result: ",languages1) 

 # Output: Language List 1: ['Python', 'PHP', 'Java'] Language List 2: ['C', 'C++', 'C#'] Language List 3: ['Scala', 'Ruby'] Result: ['Python', 'PHP', 'Java', [['C', 'C++', 'C#'], ['Scala', 'Ruby']]] 

3. Append List Elements to Another List

If you wanted to append the individual element from one list to another list you can use the extend(). This method takes the list as an argument and extends the list to separate elements and appends to the list.

 # Consider two lists languages1=['Python','PHP','Java',] languages2=['C','C++','C#'] print("Language List 1: ",languages1) print("Language List 2: ",languages2) # Append List Elements into Another List languages1.extend(languages2) print("Result: ",languages1) 

 # Output: Language List 1: ['Python', 'PHP', 'Java'] Language List 2: ['C', 'C++', 'C#'] Result: ['Python', 'PHP', 'Java', 'C', 'C++', 'C#'] 

Similarly, you can also get this output by using + operator * unpack and many more. Refer to append multiple elements to the list.

4. Using Looping with insert()

Finally, you can also achieve this by using the insert() with for loop. This is used to append a single element at a time at a specific position. Here, we will loop through the languages2 list and each element is appended to the languages1 at the end. len(languages2) returns the count of the list which is used to specify the end position.

 # Consider two lists languages1=['Python','PHP','Java',] languages2=['C','C++','C#'] print("Language List 1: ",languages1) print("Language List 2: ",languages2) # Append list elements using insert() for x in languages2: languages1.insert(len(languages1),x) print("Result: ",languages1) 

This yields the same output as above.

Conclusion

In this article, you have learned how to append the whole list as an item or element to another list using append() and also learned appending elements from one list to another using extend() and other approaches.

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Python Append List to another List without Brackets

In this Python tutorial, we will learn about the Python Append List to another List without Brackets where we will see various ways to Append a List to another List without Brackets using the examples.

Python append list to another list

Python programmers often encounter – appending one list to another. To start, let’s understand what appending a list in Python usually means.

When we talk about appending a list to another list in Python, it usually involves adding the second list as a single element at the end of the first list. This is done using the append() method. However, this method results in a nested list, i.e., a list within a list.

east_states = ['New York', 'Florida', 'Georgia'] west_states = ['California', 'Washington', 'Nevada'] east_states.append(west_states) print(east_states) 

Notice the extra brackets around the second list in the output. This means that east_states is nested inside west_states. Sometimes, you want to merge two lists without nesting, meaning you want to add each element of the second list to the first list as an individual element.

So, let’s move ahead and learn different ways to append List to another List without Brackets.

Append List to another List without Brackets in Python

Today, we’re going to dive into a common scenario American developers often deal with: adding one list to another, but without the added brackets that typically result.

To kick off, let’s imagine that we’re on a road trip, traveling through various states. We have two lists of states, one for the eastern states we’ve visited, and one for the western states.

But, this time we just want one big list of all states we’ve visited, without categorizing them as east or west. So, let’s discuss each of the methods:

Method1: Using Python Extend() Function

east_states = ['New York', 'Florida', 'Georgia'] west_states = ['California', 'Washington', 'Nevada'] east_states.extend(west_states) print(east_states) 

Now you can see, extend() adds each element of east_states to west_states resulting in a single list without extra brackets. In other words, extend() merges the two lists together. We’ve effectively created a list of all states visited during our road trip!

Method2: += operator in Python

An alternative to the extend() method is the += operator, which can be used to achieve the same effect.

east_states = ['New York', 'Florida', 'Georgia'] west_states = ['California', 'Washington', 'Nevada'] east_states += west_states print(east_states) 

As you can see, the += operator also combines the lists into one, just like extend() , without any extra brackets or nesting.

Conclusion

In conclusion, Python provides different methods to append one list to another. While append() nests the second list within the first, extend() and += operator adds the second list to the first as individual elements, removing the need for additional brackets.

You may also like to read the following Python tutorials.

I am Bijay Kumar, a Microsoft MVP in SharePoint. Apart from SharePoint, I started working on Python, Machine learning, and artificial intelligence for the last 5 years. During this time I got expertise in various Python libraries also like Tkinter, Pandas, NumPy, Turtle, Django, Matplotlib, Tensorflow, Scipy, Scikit-Learn, etc… for various clients in the United States, Canada, the United Kingdom, Australia, New Zealand, etc. Check out my profile.

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