The error message:
IndexError: pop index out of range
occurs when you try to remove an element from a list using an index that does not exist.
1. Causes and Solutions
Cause 1: Using an Out-of-Range Index with pop()
If you try to pop() an element using an index that exceeds the valid range, Python raises an IndexError.
Incorrect Code:
numbers = [10, 20, 30]
print(numbers.pop(3)) # Error: Index 3 does not exist (valid indices: 0, 1, 2)
Solution: Ensure the index is within the list’s range.
if 3 < len(numbers):
print(numbers.pop(3))
else:
print("Index is out of range")
Cause 2: Using pop() on an Empty List
If a list is empty and you try to pop() an element, this error occurs.
Incorrect Code:
empty_list = []
empty_list.pop() # Error: No elements to pop
Solution: Check if the list is non-empty before popping.
if empty_list:
empty_list.pop()
else:
print("List is empty, cannot pop")
Cause 3: Using a Loop Without Checking the List Size
If you continuously pop elements without verifying the list size, an error occurs when the list becomes empty.
Incorrect Code:
numbers = [1, 2, 3]
for _ in range(5): # Error: List has only 3 elements
numbers.pop()
Solution: Use a while loop and check the list before popping.
numbers = [1, 2, 3]
while numbers:
numbers.pop()
Cause 4: Incorrect Negative Index Usage
Negative indices start from the end (-1 refers to the last element), but if the index goes beyond the valid negative range, an error occurs.
Incorrect Code:
numbers = [10, 20, 30]
print(numbers.pop(-4)) # Error: Only -1, -2, and -3 are valid
Solution: Ensure the negative index is within range.
if -4 >= -len(numbers):
print(numbers.pop(-4))
else:
print("Negative index out of range")