Typeerror expected str bytes or os.pathlike object not nonetype

Have you ever encountered an error, like “TypeError: expected str, bytes or os.PathLike object, not NoneType”?

If so, don’t worry, you’re not alone.

This expected str, bytes or os.PathLike object, not NoneType typically occurs when we try to open a file but provide a None value for the filename.

Along with this guide, we will explore the causes of this error and provide you with practical solutions to help you fix it.

So, let’s dive in and learn how to handle this error like a pro!

What is Typeerror expected str bytes or os.pathlike object not nonetype?

The “TypeError: expected str, bytes or os.PathLike object, not NoneType” is an error that happens when we attempt to open a file but put a None value for the filename.

To fix the error, figure out where the None value comes from and correct the assignment.

Here is how the error occurs:

filename = None

# TypeError: expected str, bytes or os.PathLike object, not NoneType
with open(filename, 'r', encoding='utf-8') as f:
    lines = f.readlines()

    print(lines)

If we run this code it will raise an error.

Traceback (most recent call last):
  File "C:\Users\Windows\PycharmProjects\pythonProject1\main.py", line 4, in <module>
    with open(filename, 'r', encoding='utf-8') as f:
TypeError: expected str, bytes or os.PathLike object, not NoneType

Causes of expected str bytes or os.pathlike object not nonetype

The most common cause of None values are:

1. Functions return None implicitly.
2. Having a variable set to None.
3. A function that only returns a value when a certain value is met.
4. Assigning a variable to the result which calls a built-in function that doesn’t return anything.

Solved Typeerror expected str bytes or os.pathlike object not nonetype

The following are solutions to the causes we mention that throw the expected str bytes or os.pathlike object not nonetype.

Functions do not return anything return None.

Functions that don’t obviously return a value return None.

For example:

# this function returns None
def get_filename():
    print('example.txt')


#  TypeError: expected str, bytes or os.PathLike object, not NoneType
with open(get_filename(), 'r', encoding='utf-8') as f:
    lines = f.readlines()

    print(lines)

If we run this code it will raise an error…

 TypeError: expected str, bytes or os.PathLike object, not NoneType.

Alternatively, use a return statement to throw a value from a function.

def get_filename():
    return 'data.txt'

with open(get_filename(), 'r', encoding='utf-8') as f:
    lines = f.readlines()

    print(lines)

Check if the variable doesn’t store a None value

Meanwhile, if you need to check if the variable does not store None value prior to opening the file, use the If statement.

For example:

filename = None

if filename is not None:
    with open(filename, 'r', encoding='utf-8') as f:
        lines = f.readlines()

        print(lines)
else:
    print('filename stores a None value')

Alternatively, the variable can be able to set to a default value which is None. Just see to it you’re not storing the result on one variable.

Note: There are a lot of built-in functions wherein can change into their original object.

Check if the variable is initialized properly

Another way to fix the error is checking if the variable is initialized properly.

filename = None
with open(filename, 'r') as f:
    lines = f.readlines()

    print(lines)

This code will raise the expected str, bytes, or os.PathLike object, not NoneType error because the filename variable is set to None.

To fix this, you can make sure that the filename variable is initialized with a valid path:

filename = 'data.txt'
with open(filename, 'r') as f:
    lines = f.readlines()

    print(lines)

Output:

['Welcome to Itsourcecode!']

Anyhow, if you are finding solutions to some errors you might encounter we also have TypeError can’t concat str to bytes.

Conclusion

To conclude, the “TypeError: expected str, bytes or os.PathLike object, not NoneType” is an error that happens when we try to open a file but provide a None value for the filename.

To fix the error, figure out where the None value comes from and correct the assignment.

By trying the outlined solutions above, you can possibly fix the error.

Thank you for reading!

Why NoneType TypeErrors happen so often

Python returns None from many functions when there is nothing meaningful to return: from methods that mutate in place (list.append, dict.update), from lookups that miss (dict.get with no default), and from any function that ends without an explicit return. When you use that None as if it were the expected value, you get a TypeError.

Common triggers of NoneType TypeError

• Method chaining on mutating operations. sorted(list) returns a new sorted list, but list.sort() sorts in place and returns None. Never write x = my_list.sort().
• Print statements accidentally assigned. x = print(value) assigns None, not value.
• Missing return in a function. A function that only has if branches without returns falls through to an implicit return None.
• Dictionary lookups with missing key. value = my_dict.get(key) returns None if key is missing. Provide a default: my_dict.get(key, default_value).
• Regex match returning None. re.search returns None if no match. Guard with an if before .group().

Working diagnostic pattern

# BAD — silent None propagation
def get_config(env):
    if env == "prod":
        return {"db": "prod-cluster"}
    # No else — implicit return None

config = get_config("staging")
print(config["db"])  # TypeError: 'NoneType' object is not subscriptable

# GOOD — explicit branch handling
def get_config(env):
    if env == "prod":
        return {"db": "prod-cluster"}
    if env == "staging":
        return {"db": "staging-cluster"}
    raise ValueError(f"Unknown env: {env}")

Best practices

• Use type hints (Python 3.6+). Type-checkers like mypy or Pyright catch these before runtime.
• Prefer Optional[T] when a function may return None. Callers must handle the None case.
• Fail fast at boundaries. Raise an explicit exception in helper functions rather than returning None silently.

Glay Eliver

Programmer & Technical Writer at PIES IT Solution

Glay Eliver is a programmer and writer at PIES IT Solution, author of over 600 tutorials at itsourcecode.com. Specializes in JavaScript tutorials, Microsoft Office how-tos (Excel, Word, PowerPoint), and Python error debugging covering ImportError, TypeError, AttributeError, ModuleNotFoundError, and JavaScript ReferenceError. Authored several of the site’s highest-traffic Excel and MS Office reference articles.

Expertise: JavaScript · MS Excel · MS Word · MS PowerPoint · Python · Python ImportError · Python TypeError · Python AttributeError · ModuleNotFoundError · JavaScript ReferenceError · Pygame
 · View all posts by Glay Eliver →