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We are also using the flat attribute to get a 1D iterator over the array in order to achieve our goal. Numpy offers common operations which include concatenating regular 2D arrays row-wise or column-wise. Regular_list =, , ]ДЇlat_list = list(itertools.chain(*regular_list))ДЄgain, this would give us a flattened list as the output: Original list, , ]ДЇlatten List of Lists Using numpy ( concatenate() and flat()) This approach is ideal for transforming a 2-D list into a single flat list as it treats consecutive sequences as a single sequence by iterating through the iterable passed as the argument in a sequential manner. Which would give us the desired result: Original list, ,, 11]ДЇlatten List of Lists Using itertools ( chain()) Print( 'Transformed list', functools.reduce(operator.iconcat, regular_2D_list, )) Regular_2D_list = transform(irregular_list) def transform( nested_list): for ele in nested_list: # Transform irregular 2D list into a regular one.

The iconcat() function performs the basic operation of concatenation and is applied cumulatively to the items of a list of lists, from left to right, so as to reduce it to a single list: import functools Flatten List of Lists Using functools ( reduce() and iconcat()) You can also rely on the help of Pyhon libraries for this task. Return list_of_lists + flatten(list_of_lists) Return flatten(list_of_lists) + flatten(list_of_lists) The implementation below works both for regular and irregular list of lists: def flatten( list_of_lists): if len(list_of_lists) = 0: The 2D list can be flattened recursively as well. Which would output the following: Original list, , ] This approach provides an elegant but a less intuitive solution to create a flat list based on an existing 2D list: regular_list =, , ]ДЇlat_list = Transformed Flat List ДЇlatten List of Lists Using a List Comprehension Print( 'Transformed Flat List', flatten_list(nested_list)) # If the element is of type list, iterate through the sublist for item in element: # Iterate through the outer list for element in _2d_list:

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The code is intuitive as shown below and works for both regular and irregular lists of lists: def flatten_list( _2d_list):

This is a brute force approach to obtaining a flat list by picking every element from the list of lists and putting it in a 1D list. Flatten List of Lists Using Nested for Loops Example:, , 6] where and are of type list and 6 is of type int. Therefore, there is an irregularity in terms of the element type. Irregular List of ListsД®very element of this list is either a sublist or a non-list item (for example an integer or string). Regular List of ListsД®very element of this list is a sublist, thereby adhering to the uniformity of the element type.Д®xample:, , ] is a regular list of lists as, , is of type list. Since Python is weakly typed, you can encounter regular and irregular lists of lists. The process of flattening can be performed using nested for loops, list comprehensions, recursion, built-in functions or by importing libraries in Python depending on the regularity and depth of the nested lists. Whereas, a 2D list which is commonly known as a list of lists, is a list object where every item is a list itself - for example:, , ].ДЇlattening a list of lists entails converting a 2D list into a 1D list by un-nesting each list item stored in the list of lists - i.e., converting, , ] into. A list is the most flexible data structure in Python.