When developing programs, a bitter pill to swallow is the potentially of encountering errors. An alternative way of tackling this unavoidable encounter is by taking it as a learning challenge, and striving toward understanding and troubleshooting it to get your code running well again.
Some of the errors appear frequently, while for some, rarely. One of the errors often encountered by Python developers is the Typeerror: expected str, bytes or os.pathlike object, not nonetype.
In this guide, we take you through the whole process of understanding the error and also troubleshooting to get your code working well again.
So, let’s dive in.
I. What is Typeerror: expected str, bytes or os.pathlike object, not nonetype
Just as the name implies, the error is used to indicate that a given function or operation in your code expected a str, bytes, or os.pathlike object, but instead received a NoneType object.
It was expected that a str, bytes, and os.pathlike objects were set to be passed. str objects represent a string of characters, a bytes object, on the other hand, shows a sequence of bytes, while the os.pathlike is an object that represents the file system path. Functions and operations in Python expect that a given data type is passed to execute effectively.
Ideally, the error can occur when attempting to open a file but get a None value for its filename.
II. Causes of the Typeerror
Case 1: When you use variables that are non-assigned or uninitialized.
One of the most likely causes for the error Typeerror: expected str, bytes or os.pathlike object, not nonetype is due to non-initialized or non-assigned variables in a script that expects the programmer to pass bytes, str, or os.pathlike objects.
Here is a likely case scenario:
import os
file_loc = None
os.path.basename(file_loc)
Output:
TypeError: expected str, bytes or os.PathLike object, not NoneType
Explanation: The code snippet above entails the variable file_loc assigned to the value None. When the value is passed to the function os.path.basename(), the function expects a file path to be passed as an argument, not a null value, hence prompting the error message to be shown.
Case 2: When you use incorrect function arguments or return values
Another cause for the error message is when a function gets passed an incorrect argument data type.
For example, here is a likely case scenario that generates the error:
with open('file.txt', 'w') as file1:
file1.write('Hello, world!')
with open(file1, 'r') as file2:
print(file2.read())
Output:
TypeError: expected str, bytes or os.PathLike object, not NoneType
Explanation: The program above has a variable named file1 that has been assigned the value of a file object that gets returned by the function open(). The issue arises when it is passed as an argument to the second call to the open() function, which expects an initial file path to be passed, resulting in the error.
This pinpoints the necessity of incorporating extreme care in the return values and function arguments by ensuring that they are of the correct type.
III. Troubleshooting and Fixing the TypeError: expected str, bytes or os.PathLike object, not NoneType
Fixing the error entails first going through a few troubleshooting options. This way, you have access to a number of quick options that can fix your error.
So, here are a number of ways to troubleshoot the error TypeError: expected str, bytes or os.PathLike object, not NoneType:
a. Analyze the message deeply and trace its origin.
The initial process when you encounter the error message is to analyze the error message and look at the specific part of the code where the error occurs. The error message implies that a Nonetype was received instead of a str, bytes, or os.PathLike object. Utilizing the traceback can assist in pinpointing the exact cause of the error.
b. Verify the data types or presence of None values.
The next step entails trying to identify the variables or function arguments that have been assigned the None value. Are there instances where you have passed a Nonetype instead of the expected types? Verify that the data types you are trying to use comply with the anticipated functions or operations.
c. Make the needed corrections to handle the error and defend against programming techniques.
Finally, you have to use the findings that you have gained from the previous steps to adopt error handling or defensive programming techniques. Use defensive coding endeavors such as validating the inputs to your code or error handling endeavors to prevent encountering the error again.
IV. Practical Examples
Below are a number of ways based on how you can go about solving the error based on the initial error-generating code:
Example 1:
import os
file_loc = None
os.path.basename(file_loc)
The above program generated the error because the file_loc variable has been assigned the value None. Now, we need to assign a legitimate file location to the variable for it to execute effectively, as shown below:
import os
file_loc = 'NP1/Text1.txt'
os.path.basename(file_loc)
The program now executes effectively and there are presently no error messages.
Example 2:
On the other hand, we can solve the earlier error by ensuring that the open() function receives a valid file path. The following program now works effectively. Here it is:
with open('file.txt', 'w') as file1:
file1.write('Hello, world!')
with open('file.txt', 'r') as file2:
print(file2.read())
Output:
Hello, world!
V. Conclusion
Generally, the Typeerror: expected str, bytes or os.pathlike object, not nonetype is just as the message implies, as it results from the argument expecting a str, bytes, or an os.pathlike object, but it is instead passed a Nonetype object.
It is crucial to comprehend the specific cause of the error and the steps toward solving it to get the program running well again.
By following and implementing the steps shown in this tutorial, you should have your program running well again with no issues.
