Coding⏱️ 2 min read📅 2026-05-30

How to Fix: UnicodeDecodeError: 'charmap' codec can't decode byte X in position Y: character maps to <undefined>

UnicodeDecodeError occurs when Python tries to decode a byte that doesn't match any character in the specified encoding.

Quick Answer: Use the correct encoding for your text file, such as 'utf-8' or 'latin1', and handle potential errors with try-except blocks.

The error you're encountering is due to the Python interpreter's default encoding being unable to decode a specific character in your text file. This issue can be resolved by specifying an appropriate encoding when reading the file.

🛑 Root Causes of the Error

  • Using an encoding that doesn't support the characters present in your file.

🔧 Proven Troubleshooting Steps

Method 1: Specifying the Correct Encoding

  1. Step 1: Open your file in a text editor and identify its encoding. This can usually be done by looking at the file's metadata or using an online tool.

Method 2: Using the `errors` Parameter

  1. Step 1: When opening your file, specify the encoding using the `encoding` parameter. For example, if you suspect your file is encoded in UTF-8, use `open('filename.txt', 'r', encoding='utf-8').

💡 Conclusion

By identifying the correct encoding for your file and specifying it when reading, you can prevent this error from occurring. Always ensure that your Python interpreter's default encoding is set to a more permissive setting to handle unexpected characters.

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