If you are a Python developer, you may have encountered the error message “NameError name ‘copy’ is not defined” while working with the copy module in Python. In this tutorial, we will explore the possible causes of this error and provide step-by-step instructions on how to fix it.
We will cover common causes of the error and provide solutions to help you get your code up and running quickly. So, let’s get started!
Why does the NameError: name 'copy' is not defined error occur?
This error occurs when you try to use the copy library in your Python code, but Python cannot find the copy module in its namespace. The following are some of the scenarios in which this error usually occurs.
- You have not imported the copy module.
- You have imported the copy module using a different name.
How to fix the NameError: name 'copy' is not defined?
The copy module in Python provides a way to create copies of objects in Python. This module is useful when we want to create a new object with the same values as an existing object without modifying the original object. Since this library is part of the Python Standard Library, you don’t need to separately install it. You can simply import it and start using it.
It provides both shallow and deep copy operations for objects. Shallow copy creates a new object which stores the reference of the original elements, whereas deep copy creates a new object and recursively adds the copies of nested objects.
Let’s now look at the above scenarios that may result into the above error in detail.
The copy module is not imported
It can happen that you are trying to use the copy module without even importing it. This is because Python does not recognize the copy library and its functions until it is imported into the code.
For example, let’s try to use the copy module without importing it and see what we get.
# note that copy is not imported # create a list original_list = [1, 2, 3, [4, 5]] # create a deep copy of the list deep_copy = copy.deepcopy(original_list) print(deep_copy)
Output:
---------------------------------------------------------------------------
NameError Traceback (most recent call last)
Cell In[1], line 7
4 original_list = [1, 2, 3, [4, 5]]
6 # create a deep copy of the list
----> 7 deep_copy = copy.deepcopy(original_list)
9 print(deep_copy)
NameError: name 'copy' is not defined
We get a NameError stating that the name copy is not defined. To use the copy library, you need to import it first.
import copy # create a list original_list = [1, 2, 3, [4, 5]] # create a deep copy of the list deep_copy = copy.deepcopy(original_list) print(deep_copy)
Output:
[1, 2, 3, [4, 5]]
Here, we are importing the copy module first and then using it to create a deep copy of the original list. You can see that we did not get any errors here.
You can also get a NameError if you are importing only specific parts of the library and then trying to access the entire copy library. For example –
from copy import deepcopy # create a list original_list = [1, 2, 3, [4, 5]] # create a deep copy of the list deep_copy = copy.deepcopy(original_list) print(deep_copy)
Output:
---------------------------------------------------------------------------
NameError Traceback (most recent call last)
Cell In[1], line 7
4 original_list = [1, 2, 3, [4, 5]]
6 # create a deep copy of the list
----> 7 deep_copy = copy.deepcopy(original_list)
9 print(deep_copy)
NameError: name 'copy' is not defined
We get a NameError here because we are importing only the deepcopy() function from the copy library but we are trying to access the entire library. To resolve the above error, either only use the specific method imported or import the copy library altogether.
The copy module is imported using a different name
If you import the copy module using a different name, for example import copy as cp, and then try to use the name “copy” to use it, you will get a NameError because the name “copy” is not defined in your current namespace.
Let’s look at an example.
import copy as cp # create a list original_list = [1, 2, 3, [4, 5]] # create a deep copy of the list deep_copy = copy.deepcopy(original_list) print(deep_copy)
Output:
---------------------------------------------------------------------------
NameError Traceback (most recent call last)
Cell In[1], line 7
4 original_list = [1, 2, 3, [4, 5]]
6 # create a deep copy of the list
----> 7 deep_copy = copy.deepcopy(original_list)
9 print(deep_copy)
NameError: name 'copy' is not defined
We get a NameError: name 'copy' is not defined. This is because we have imported the copy module with the name cp but we’re trying to use it using the name copy.
To fix this error, you can either access copy using the name that you have used in the import statement or import copy without an alias.
import copy as cp # create a list original_list = [1, 2, 3, [4, 5]] # create a deep copy of the list deep_copy = cp.deepcopy(original_list) print(deep_copy)
Output:
[1, 2, 3, [4, 5]]
In the above example, we are importing copy as cp and then using cp to access the copy module’s methods.
Alternatively, as seen in the example in the previous section, you can import copy without any aliases and simply use copy to avoid the NameError.
Conclusion
In conclusion, encountering a NameError: name 'copy' is not defined error can be frustrating, but it is a common issue that can be easily fixed. By ensuring that the copy module is imported correctly and that the correct syntax is used when calling its functions, you can avoid this error and successfully execute your code.
You might also be interested in –
- How to Fix – NameError name ‘pprint’ is not defined
- How to Fix – NameError name ‘statistics’ is not defined
- How to Fix – NameError name ‘random’ is not defined
