How to Modify Python Code to Read Lines from a File as a List

Learn how to read lines from a file as a list in Python to avoid the 'TypeError: '_io.TextIOWrapper' object is not subscriptable' error.
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When working with file operations in Python, you may encounter the error: TypeError: '_io.TextIOWrapper' object is not subscriptable. This occurs when you attempt to access elements of a file object directly as if it were a list. To avoid this error, you need to read the lines from the file into a list first. Here’s how you can do it:

Understanding the Error

The TypeError in question arises due to the misuse of file objects. A file object returned by open() is not inherently a list or sequence; you can't directly index into it.

Example of Error-Prone Code

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How to Fix It

To fix this, you need to convert the file object into a list by reading its lines using the readlines() method. Here's how:

[[See Video to Reveal this Text or Code Snippet]]

In this corrected version, the readlines() method reads the file's contents and stores each line as an element in a list. You can then safely access elements of this list using indices.

Alternative Approach: List Comprehension

Another efficient way to read lines into a list is using a list comprehension with readline() method in a loop:

[[See Video to Reveal this Text or Code Snippet]]

Using with open, this approach ensures the file is properly closed after reading, making the code more robust.

Summary

By reading a file’s lines into a list, you can manipulate and access individual lines directly. This adjustment avoids the TypeError: '_io.TextIOWrapper' object is not subscriptable and makes your file handling code more effective in Python.