[Tut] [Resolve] IndexError: List Assignment Index Out of Range

[Tut] [Resolve] IndexError: List Assignment Index Out of Range - Printable Version

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[Tut] [Resolve] IndexError: List Assignment Index Out of Range - xSicKxBot - 04-19-2020

[Resolve] IndexError: List Assignment Index Out of Range

When does the

Code:
IndexError: list assignment index out of range

appear?

Python throws an

Code:
IndexError

if you try to assign a value to a list index that doesn’t exist, yet. For example, if you execute the expression

Code:
list[1] = 10

on an empty

Code:
list

, Python throws the

Code:
IndexError

. Simply resolve it by adding elements to your list until the index actually exists.

[Image: image-2.png]

Here’s the minimal example that throws the IndexError:

Code:
lst = []
lst[1] = 10

If you run this code, you’ll see that Python throws an

Code:
IndexError

Code:
Traceback (most recent call last): File "C:\Users\xcent\Desktop\code.py", line 2, in <module> lst[1] = 10
IndexError: list assignment index out of range

You can resolve it by adding two “dummy” elements to the list so that the index 1 actually exists in the list:

Code:
lst = [None, None]
lst[1] = 10
print(lst)

Now, Python will print the expected output:

Code:
[None, 10]

Try to fix the

Code:
IndexError

in the following interactive code shell:

https://repl.it/@finxter/RemarkablePungentCensorware?lite=true

Exercise: Can you fix this code?

So what are some other occurrences of the IndexError?

IndexError in For Loop

Frequently, the

Code:
IndexError

happens if you use a

Code:
for

loop to modify some list elements like here:

Code:
# WRONG CODE:
lst = []
for i in range(10): lst[i] = i
print(lst)

Again, the result is an

Code:
IndexError

Code:
Traceback (most recent call last): File "C:\Users\xcent\Desktop\code.py", line 4, in <module> lst[i] = i
IndexError: list assignment index out of range

You modify a list element at index

Code:
i

that doesn’t exist in the list. Instead, create the list using the

Code:
list(range(10))

list constructor.

Code:
# CORRECT CODE:
lst = list(range(10))
print(lst)
# [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

Where to Go From Here?

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