Why Does `open()` in Python Throw a `FileNotFoundError`, and How Can I Fix It?

Resolving "open() gives FileNotFoundError / IOError" for Nonexistent Files

When attempting to load files using the open() function in Python, you may encounter a "FileNotFoundError / IOError" error with the message "[Errno 2] No such file or directory." This error signifies the inability of the script to locate the specified file.

To delve into the root cause, it's crucial to understand how Python locates files:

• Absolute path: Begins with the computer's root directory, such as 'C:Pythonscripts' in Windows.
• Relative path: Does not start with the root directory and is relative to the "working directory."

When using open('recentlyUpdated.yaml'), Python assumes a relative path and searches within the current working directory. To diagnose the issue:

• Verify file existence: Use os.listdir() to list files in the current working directory and ensure the file with the correct extension exists.
• Confirm current directory: Use os.getcwd() to verify the expected directory, as code launched from an IDE may have a different working directory.

Resolutions:

1. Change current working directory: Use os.chdir(dir) to navigate to the directory containing the file, then open it with open("file.txt").
2. Provide absolute path: Specify the complete path to the file in the open call, such as open(r'C:Folderfile.txt').

Note:

• Use raw strings (r"") for paths with backslashes, e.g., r'C:Python32'.
• Forward-slashes work on Windows 'C:/Python32' and do not require escaping.

• Example: Assuming file.txt is found in C:Folder, you can open it as:

  • os.chdir(r'C:Folder')
    open('file.txt') # relative path
  • open(r'C:Folderfile.txt') # absolute path

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