How to fix PermissionError when working with files in Python

The aim of this page📝 is to explain how to fix a PermissionError when working with files in Python. Previously I showed How to Write Unit Tests for Custom Context Manager in Python which is just an illustration of fixing little problems along the way.

Pavol Kutaj

·

Follow

1 min read

·

Jul 13, 2023

--

Listen

Share

• The error occurs when a file is being used by another process and cannot be accessed.
• This can happen if the file is not closed properly before it is removed.
• To fix the issue, make sure to close the file before removing it.
• Here’s the original code that caused the error:

""" CODE """
@contextmanager
def handle_patching(schema: dict) -> None:
    try:
        with open("temp_schema.json", mode="wt", encoding="utf-8") as temp_schema:
            json.dump(schema, temp_schema, indent=4)
        yield
    finally:
        # TODO: Send a PUT request of the patched schema
        os.remove("temp_schema.json")

""" TEST FAILING WITH `PermissionError` """
def test_handle_patching():
    TEMP_SCHEMA_FILENAME = "temp_schema.json"
    schema = {}
    with push_and_pop_path(MODULE_PATH):
        with handle_patching(schema):
            assert TEMP_SCHEMA_FILENAME in os.listdir()
            assert "{}" in open(TEMP_SCHEMA_FILENAME).read()
        assert TEMP_SCHEMA_FILENAME not in os.listdir()

• And here’s an example of how to fix the issue:

def test_handle_patching():
    TEMP_SCHEMA_FILENAME = "temp_schema.json"
    schema = {}
    with push_and_pop_path(MODULE_PATH):
        with handle_patching(schema):
            assert TEMP_SCHEMA_FILENAME in os.listdir()
            with open(TEMP_SCHEMA_FILENAME) as f:
                assert "{}" in f.read()
        assert TEMP_SCHEMA_FILENAME not in os.listdir()

• This ensures that the file is closed before it is removed and prevents the PermissionError.