A Guide to Flatten List & List of Lists in Python

Changing a second array in a single 1D array is named flatten. There are lots of approaches to resolve the issue.

We’ll discover a few of them on this tutorial.

Let’s have a look at an instance.

Enter

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

Exit

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

#1. Loops

The most typical approach to resolve the issue is to make use of loops. I believe most of you have already got it. Let’s have a look at the steps to resolve the issue utilizing loops.

• Initialize the record of dummy information lists and identify it as information.
• Now initialize an empty record named flat_list.
• Repeat throughout the information.
  • Extract all components from the present record.
  • Add them to the flat_list utilizing the add record methodology.
• Print the outcome.

See the code beneath for the issue.

# initializing the information and an empty record
information = [[1, 2, 3], [4, 5], [6, 7, 8, 9, 10]]
flat_list = []

# iterating over the information
for merchandise in information:
    # appending components to the flat_list
    flat_list += merchandise

# printing the resultantn flat_list
print(flat_list)

You should use one other loop so as to add sublist components flat_list as an alternative of a concatenation operator. We will additionally use record comprehensions as an alternative of loops.

Each do the identical job. Let us take a look at the subsequent approach to resolve the issue.

#2. Itertools – Chain

We’ll use a way referred to as chain by itertools built-in module.

The tactic chain iterates over every sublist and returns the weather till there are not any sublists left. It returns an iterable that we have to convert into an inventory.

Let’s have a look at what steps are wanted to resolve the issue.

• Initialize the record of dummy information lists and identify it as information.
• Get the flatten iterable utilizing itertools.chain(*information).
• Convert the ensuing iterable into an inventory.
• Print the flatten record.

You’ll be able to undergo the code within the snippet beneath.

# importing the module
import itertools

# initializing the information
information = [[1, 2, 3], [4, 5], [6, 7, 8, 9, 10]]

# flattening the record and storing the outcome
flat_list = itertools.chain(*information)

# changing iterable to record and printing
print(record(flat_list))

#3. Flatten multi-level lists

We have seen easy methods to flatten an inventory of lists. The above strategies we mentioned to flatten the record won’t work for multi-level lists. Let’s have a look at an instance.

Enter

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

Exit

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

Since we do not know the depth of the lists earlier than this system, we now have to make use of recursion to resolve the issue.

• Initialize the information as proven within the instance and identify it as information.
• Initialize an empty record referred to as flat_list.
• Write a perform referred to as flatten_list.
  • Repeat the weather of the given record.
  • If the ingredient is an inventory, recursively name the identical perform once more.
  • If the ingredient just isn’t an inventory, add the ingredient to it flat_list.
• Name the perform with information.
• The perform fills all components within the flat_list record.
• Press the flat_list to verify the output.

Aid! many steps to code. Don’t worry. Changing the above statements into code ought to take no various minutes.

# initializing the information and empty record
information = [1, [2, 3, [4, 5]], 6, [[7], [8, 9]]]
flat_list = []

# perform
def flatten_list(information):
    # iterating over the information
    for ingredient in information:
        # checking for record
        if sort(ingredient) == record:
            # calling the identical perform with present ingredient as new argument
            flatten_list(ingredient)
        else:
            flat_list.append(ingredient)

# flattening the given record
flatten_list(information)

# printing the flat_list
print(flat_list)

Please be aware that we now have not transformed the present record. As an alternative, we created a brand new record with the given record ingredient.

Conclusion

I hope you loved the tutorial. There could also be many different methods to flatten an inventory in Python, however I discovered the above to be most likely the simplest.

Have enjoyable coding 🙂