OSError: Invalid argument when opening file

The error OSError: Invalid argument occurs when opening a file due to incorrect parameters or system-related issues. This guide will cover the common causes and solutions for fixing this error.

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1. Common Causes and Fixes

Cause 1: Using Invalid File Paths

If the file path is incorrect or contains unsupported characters, Python may raise an OSError.

❌ Example:

with open("C:\new\file.txt", "r") as file:
    data = file.read()

This fails because \n is interpreted as a newline.

Solution: Use raw strings (r"") or double backslashes (\\):

with open(r"C:\new\file.txt", "r") as file:
    data = file.read()

or

with open("C:\\new\\file.txt", "r") as file:
    data = file.read()

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Cause 2: Passing an Invalid File Descriptor

Opening a file using an invalid descriptor (e.g., closed file descriptor) leads to this error.

Example:

import os
fd = os.open("example.txt", os.O_RDWR)
os.close(fd)
with open(fd, "r") as file:  # Trying to reuse a closed file descriptor
    data = file.read()

Solution: Ensure the file descriptor is valid:

import os
fd = os.open("example.txt", os.O_RDWR)
with open(fd, "r", closefd=False) as file:  # Keep descriptor open
    data = file.read()
os.close(fd)

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Cause 3: Trying to Open a Special System File

Some files like /dev/null (Linux) or NUL (Windows) can’t be opened normally.

Example:

with open("/dev/null", "w") as file:
    file.write("Test")

Solution: Ensure you’re opening valid, regular files, not system files.

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Cause 4: Incorrect File Opening Modes

Opening a binary file in text mode or vice versa can cause an OSError.

Example:

with open("binaryfile.bin", "r") as file:  # Using "r" instead of "rb"
    data = file.read()

Solution: Use the correct mode:

with open("binaryfile.bin", "rb") as file:  # Use "rb" for binary files
    data = file.read()

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Cause 5: File Too Large for OS Limits

Some operating systems have file size limits, and trying to open a very large file may cause this error.

Solution: Try reading the file in chunks instead of loading it all at once:

with open("large_file.txt", "r") as file:
    for line in file:
        print(line.strip())  # Process line by line

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Cause 6: Using an Invalid Buffering Value

The buffering argument in open() should be 0, 1, or a positive integer. Passing an invalid value raises an error.

Example:

with open("example.txt", "r", buffering=-1) as file:
    data = file.read()

Solution: Use valid buffering values:

with open("example.txt", "r", buffering=1) as file:  # Use 0, 1, or a positive integer
    data = file.read()

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Cause 7: Invalid Encoding Type

Using an incorrect or unsupported encoding can lead to OSError.

Example:

with open("example.txt", "r", encoding="unsupported-encoding") as file:
    data = file.read()

Solution: Use a standard encoding:

with open("example.txt", "r", encoding="utf-8") as file:
    data = file.read()

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Cause 8: Corrupted File System or Hardware Issues

If the file system is corrupted, Python may fail to open files.

Solution:

• Check disk space: Run df -h (Linux/macOS) or dir (Windows).
• Run a disk check:
  • Windows: chkdsk /f
  • Linux/macOS: fsck

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2. Summary of Fixes

Issue	Fix
Incorrect file path	Use raw strings (r"") or double backslashes (\\)
Invalid file descriptor	Ensure the descriptor is open before using it
Opening system files	Use only regular files
Incorrect file mode	Use "rb" for binary files and "r" for text files
Large file size	Read in chunks using for line in file:
Invalid buffering argument	Use 0, 1, or a positive integer
Unsupported encoding	Use "utf-8" or a valid encoding
File system issues	Check disk space and run chkdsk or fsck