# Here is how to make a flat list out of a list of lists in Python.

```import itertools

# Define a list of lists
list_of_lists = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

# Flatten the list of lists using itertools.chain()
flattened_list = list(itertools.chain(*list_of_lists))

# Print the flattened list
print(flattened_list) # Output: [1, 2, 3, 4, 5, 6, 7, 8, 9] ```

Output

Explanation

To make a flat list out of a list of lists in Python, you can use the itertools.chain() function from the itertools module. This function takes a list of lists as an argument and returns an iterator that yields the elements of the inner lists one at a time.

In the example above, the my_lists variable contains a list of three lists, each containing three numbers. The itertools.chain() function is used to flatten this list of lists into a single list, which is then stored in the flattened_list variable. The flattened_list variable contains the elements from all of the sub-lists in the original list, in the order they appear.

Another way to flatten a list of lists in Python is to use a list comprehension. For example:

```# Define a list of lists
list_of_lists = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

# Use a list comprehension to make a flat list
flat_list = [x for sublist in list_of_lists for x in sublist]

print(flat_list) # Output: [1, 2, 3, 4, 5, 6, 7, 8, 9 ]
```

In this example, the itertools.chain() function is used to flatten the nested_lists list of lists. The chain() function takes the nested_lists list as its argument, and returns an iterator that yields the elements from all of the lists in nested_lists. This iterator is then passed to the list() function, which creates a new list from the iterator's elements. The resulting list, which is stored in the flattened_list variable, contains all of the elements from the original lists, in the same order as they appeared in the original lists.

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