List Head and Tail in One Line Python

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Problem Formulation: How to assign the first list element to the variable head and the remaining elements to the variable tail?

Let’s have a look at the two most Pythonic solutions to this one-liner programming challenge! 🙂

Method 1: Unpacking and Multiple Assignment

Given a list.

The most Pythonic way to unpack the first element into one variable head and the remaining elements into variable tail, assigns the list to the tuple of the head variable and the asterisked *tail variable like so:

head, *tail = my_list

Here’s a minimal example:

my_list = ['Alice', 'Bob', 'Carl', 'Denise']
head, *tail = my_list

print(head)
# Alice

print(tail)
# ['Bob', 'Carl', 'Denise']

The feature used is called iterable unpacking and it is used to assign an iterable to multiple variables. How?

💡 By specifying the variables on the left of an assignment operator = and the iterable on the right.

Python attempts to find a suitable mapping from the iterable on the right to the variables on the left.

If one of the variables on the left of the assignment = operator is asterisked like *tail, this variable captures “all remaining iterable values” that cannot be captured by the other variables.

Thus, the unpacked form tail now contains an iterable (list) of all remaining values not captured by any other variable on the left.

Method 2: Indexing and Slicing

Given a list.

To unpack the first element into one variable head and the remaining elements into variable tail, use indexing and slicing like so:

head, tail = my_list[0], my_list[1:]

Here’s a minimal example:

my_list = ['Alice', 'Bob', 'Carl', 'Denise']
head, tail = my_list[0], my_list[1:]

print(head)
# Alice

print(tail)
# ['Bob', 'Carl', 'Denise']
  • The variable head contains only the first element of the list—accessed via the zero-based indexing scheme lst[0].
  • The variable tail contains all remaining elements from the second to the last list element—accessed via the slicing operation my_list[1:] with default stop index (i.e., slices all the way to the right).

You can learn more about slicing in this tutorial—feel free to watch the video too!

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