Typeerror: bad operand type for unary -: ‘list’ [SOLVED]

The “typeerror: bad operand type for unary -: ‘list'” is an error message in Python.

Are you tired and exhausted from trying to figure out how to solve it? Well, this article is your answer.

This is because in this article we are going to explore the solutions to troubleshoot the “bad operand type for unary ‘list'” error message.

Continue reading as we are going to discuss what this error is all about, why it occurs, and certainly the effective solutions.

Before we dive into the solution, it is good to have a better understanding of this error.

So that next time if you experience it in the future, you already know how to troubleshoot it.

What is “typeerror: bad operand type for unary -: ‘list'” error message?

The “typeerror: bad operand type for unary -: ‘list'” is a common error that occurs when you’re trying to use the unary minus (-) operator on a list, which is not a valid operation.

In addition to that, this error happens when Python encounters an incompatible operand type for the unary minus (-) operator, which is designed to work with numbers but not with lists.

For further understanding…

The unary minus operator in Python is designed to work with numbers, allowing you to perform negation or subtraction operations.

However, it cannot be applied directly to a list, which is a collection of elements.

Why does this error occurs?

The “bad operand type for unary ‘list'” error message occurs for various reasons, such as:

→ When you’re not using the unary minus operator correctly in your code, such as by applying it to a list instead of a number.

→ When the list contains elements of unexpected data types, such as strings or other non-numeric values. Python may not be able to perform the unary minus operation and raise this error.

→ When you’re trying to perform operations that involve mismatched data types, such as subtracting a list from an integer or vice versa.

→ When there are incorrect syntax or typo in your code, such as missing parentheses or improper logic, it can lead to this error.

How to fix typeerror: bad operand type for unary -: ‘list’

In this section, you’ll see the different solutions to the “bad operand type for unary ‘list'” error message that keeps on bothering you.

You may select which solution you will use to fix the error. All of the solutions below are effective in getting rid of the error.

1. Convert the list to a numeric data type

Convert the list to a numeric data type before applying unary minus.

You can easily convert the list elements to a numeric data type, such as integers or floats, before applying the unary minus operator.

For example:

sample_list = ['10', '20', '30', '40', '50']
result = [-int(num) for num in sample_list]

print(result)

Output:

[-10, -20, -30, -40, -50]

2. Use a loop to apply unary minus to list elements individually

You can simply use a loop to iterate through each element in the list and apply the unary minus operator to them individually.

sample_list = [10, 20, 30, 40, 50]
result = []
for num in sample_list:
    result.append(-num)

print(result)

Output:

[-10, -20, -30, -40, -50]

3. Use a list Comprehension to apply unary minus to list elements

You can use a list comprehension to apply the unary minus operator to list elements on a single line. That is an easy way to create a new list.

sample_list = [10, 20, 30, 40, 50]
result = [-num for num in sample_list]

print(result)

Output:

[-10, -20, -30, -40, -50]

4. Convert the list to a compatible data type

In order to use the unary minus operator on a list, you need to convert it first to a compatible data type, such as a NumPy array or a Pandas DataFrame.

import numpy as np

sample_list = [10, 20, 30, 40, 50]
my_array = np.array(sample_list)
result = -my_array
print(result)

Output:

[-10 -20 -30 -40 -50]

5. Use map() function

The map() function can also be used to apply a function to each element in a list.

sample_list = [10, 20, 30, 40, 50]
result = list(map(lambda x: -x, sample_list))
print(result)

Output:

[-10, -20, -30, -40, -50]

Frequently Asked Questions (FAQs)

Conclusion

By executing the different solutions that this article has already given, you can definitely fix the “typeerror: bad operand type for unary -: ‘list'”  error in Python.

We are hoping that this article provides you with sufficient solutions.

You could also check out other “typeerror” articles that may help you in the future if you encounter them.

• Typeerror: super expression must either be null or a function
• Typeerror: ‘index’ object is not callable
• Typeerror: ‘bytes’ object cannot be interpreted as an integer

Thank you very much for reading to the end of this article.