Last modified: Dec 15, 2025 By Alexander Williams

Fix Python AttributeError 'list' No 'copy'

Python errors can be confusing. The AttributeError is common.

It happens when you call a method on the wrong data type.

This guide explains the 'list' object has no attribute 'copy' error.

We will show you why it happens and how to fix it.

Understanding the AttributeError

An AttributeError signals a failed attribute reference.

You try to access an attribute or method an object does not have.

For lists, the copy method exists in Python 3.

So this error often means your variable is not a list anymore.

It was likely reassigned to a different type.

Common Cause: Variable Reassignment

The main cause is accidentally changing a variable's type.

You might start with a list. Later, you assign a new value.

This new value could be an integer, string, or tuple.

These types do not have a copy method.

Let's look at a typical mistake.


# Example causing the error
my_list = [1, 2, 3]
print("Original list:", my_list)

# Later, we mistakenly reassign the variable
my_list = "Hello, World!"  # Now it's a string
print("Variable is now:", my_list)

# Trying to copy a string with .copy() causes the error
new_list = my_list.copy()  # AttributeError!


Original list: [1, 2, 3]
Variable is now: Hello, World!
Traceback (most recent call last):
  File "script.py", line 9, in 
    new_list = my_list.copy()
AttributeError: 'str' object has no attribute 'copy'

The error says 'str' object has no attribute 'copy'.

This confirms my_list is now a string.

It is no longer the list you thought it was.

This is a classic debugging scenario.

How to Diagnose the Problem

First, check the variable's type before the error line.

Use the type() built-in function.

Print the variable's type and its current value.

This will reveal the unexpected type change.


my_list = [1, 2, 3]
# ... some code in between ...
my_list = 42  # Accidental reassignment

# Diagnostic print statements
print("Type of my_list:", type(my_list))
print("Value of my_list:", my_list)

# The line that will fail
new_list = my_list.copy()


Type of my_list: 
Value of my_list: 42
Traceback (most recent call last):
  File "script.py", line 10, in 
    new_list = my_list.copy()
AttributeError: 'int' object has no attribute 'copy'

The output shows my_list is an integer.

Integers do not have a copy method. This pinpoints the bug.

You must find where the variable was reassigned.

Search your code for all assignments to that variable name.

Correct Solutions and Best Practices

Once you find the wrong assignment, you must correct it.

Ensure the variable remains a list if you need to call .copy().

Here are the proper ways to copy a list in Python.

1. Use the list.copy() Method (Python 3)

For a list variable, .copy() creates a shallow copy.

This is the intended method that should work.


original_list = [10, 20, 30]
copy_list = original_list.copy()  # Correct usage

print("Original:", original_list)
print("Copy:", copy_list)

# Modify the copy to show independence
copy_list.append(40)
print("Original after mod:", original_list)
print("Copy after mod:", copy_list)


Original: [10, 20, 30]
Copy: [10, 20, 30]
Original after mod: [10, 20, 30]
Copy after mod: [10, 20, 30, 40]

2. Use the list() Constructor

You can create a new list from the old one.

Pass the original list to the list() function.

This also performs a shallow copy.


original = ['a', 'b', 'c']
new_list = list(original)  # Creates a copy
print(new_list)


['a', 'b', 'c']

3. Use Slicing [:]

List slicing is a classic Python technique.

Using [:] creates a copy of the entire list.


data = [True, False, True]
data_copy = data[:]  # Copy via slicing
print(data_copy)


[True, False, True]

Preventing Variable Reassignment Bugs

Use descriptive variable names. Avoid generic names like 'list' or 'data'.

Names like user_ids or price_list are clearer.

Be careful in loops and function scope.

A variable inside a function might shadow a global one.

Also, watch for operations that change type.

For example, using .sort() returns None.

Assigning its result changes your variable.

Similar issues occur with methods like append or remove.

If you face a Fix Python List AttributeError 'remove', the cause is often the same.

You might be calling it on a non-list object.

Conclusion

The 'list' object has no attribute 'copy' error is a type issue.

Your variable is not a list when you think it is.

Diagnose with type() and print statements.

Find where the variable was reassigned incorrectly.

To copy a list, use .copy(), list(), or slicing [:].

Use clear variable names to prevent these bugs.

Understanding this error helps you fix similar ones.

Like errors with pop, remove, or update on wrong types.

Happy coding and careful debugging!