Solve Python error: IndexError: list index out of range

Solution to Python error: IndexError: list index out of range

We often encounter various errors when writing Python programs. One of the common errors is " IndexError: list index out of range". This error usually means that you are trying to access an index in the list that does not exist. In this article, I will explain the cause of this error and give a few possible solutions.

First, let's look at a simple example code that will throw an "IndexError: list index out of range" error when we try to access a non-existent index:

my_list = [1, 2, 3]
print(my_list[3])

This code , we try to access the 4th element of the my_list list, but the list only has 3 elements, so the "IndexError: list index out of range" error will be raised.

There are usually two reasons why this error occurs:

1. An index that exceeds the list range is accessed.
2. An empty list was accessed.

For the first case, we can solve it by ensuring that the index value is within the legal range of the list. Before accessing the list elements, we can use the len() function to get the length of the list and make a judgment to ensure that the index value does not exceed the range. Modify the above example code as follows:

my_list = [1, 2, 3]
index = 3

if index < len(my_list):
    print(my_list[index])
else:
    print("索引超出范围")

In this example, we ensure that the index does not go out of range by comparing the index value to the length of the list. If the index is legal, print the corresponding element value; otherwise, print the "index out of range" prompt.

For the second case, where an empty list is accessed, we can first check whether the list is empty before trying to access the elements of the list. Modify the sample code as follows:

my_list = []
index = 0

if len(my_list) > 0:
    print(my_list[index])
else:
    print("列表为空")

In this example, we first use the len() function to check whether the length of the list is greater than 0. If it is greater than 0, then try to access the element; otherwise, print "List is empty" prompt.

In addition to the above solutions, there are some other processing methods that can be considered:

1. Use the try-except exception handling mechanism to catch and handle IndexError. The example is as follows:

my_list = [1, 2, 3]
index = 3

try:
    print(my_list[index])
except IndexError:
    print("索引超出范围")

In this example, we use the try-except statement block to catch the IndexError exception. If the exception is caught, except## is executed. #Code in statement block.

When writing code, carefully check the value range of each index to ensure that it does not exceed the index range of the list.

To summarize, when the "IndexError: list index out of range" error occurs, we need to consider two situations: accessing an index that exceeds the list range and accessing an empty list. You can use conditional judgment,

len() function, exception handling, etc. to solve this error. At the same time, when writing code, you need to carefully check the value range of the index to avoid this error.

I hope the solution in this article will help you solve the "IndexError: list index out of range" error.

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