How to Create Variable-Sized Lists in Python and Avoid IndexError?

Creating Variable-Sized Lists in Python

You want to create an empty list in Python with a specific capacity to store elements. Upon attempting to assign values to this list, you encounter an IndexError. This error arises because Python lists behave differently from arrays in other languages.

Why the Code Produces an Error

The code:

xs = list()
for i in range(0, 9):
   xs[i] = i

attempts to access an unassigned element of the list (xs[i]). To fix this, use xs.append(value) to add elements to the end of the list instead:

xs = []
for i in range(0, 9):
   xs.append(i)

Creating an Empty List with a Given Size

To create an empty list with a fixed size, you can use the following methods:

• 1. Using [None] * n: Create a list with n None values:

xs = [None] * 10

• 2. Using range(x) (Python 2.X only): Create a list from 0 to x-1:

xs = range(10)

• 3. Using a function: Define a function to generate a list:

def create_list(size):
    xs = []
    for i in range(size):
        xs.append(i)
    return xs

xs = create_list(10)

• 4. List comprehension: Use list comprehension to create a list:

xs = [i for i in range(10)]

By employing one of these methods, you can reliably create empty lists of variable sizes in Python.

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