This content originally appeared on DEV Community 👩💻👨💻 and was authored by Reza Lavarian
✋ Update: This post was originally published on my blog decodingweb.dev, where you can read the latest version for a 💯 user experience. ~reza
The “TypeError: ‘list’ object is not callable” error occurs when you try to call a list (list object) as if it was a function!
Here’s what the error looks like:
Traceback (most recent call last):
File "/dwd/sandbox/test.py", line 6, in
more_items = list(range(11, 20))
^^^^^^^^^^^^^^^^^^^
TypeError: 'list' object is not callable
Calling a list object as if it's a callable isn't what you'd do on purpose, though. It usually happens due to a wrong syntax or overriding a function name with a list object.
Let's explore the common causes and their solutions.
How to fix TypeError: 'list' object is not callable?
This TypeError happens under various scenarios:
- Declaring a variable with a name that's also the name of a function
- Indexing a list by parenthesis rather than square brackets
- Calling a method that's also the name of a property
- Calling a method decorated with
@property
Declaring a variable with a name that's also the name of a function: A Python function is an object like any other built-in object, such as str, int, float, dict, list, etc.
All built-in functions are defined in the builtins module and assigned a global name for easier access. For instance, list refers to the __builtins__.list function.
That said, overriding a function (accidentally or on purpose) with any value (e.g., a list object) is technically possible.
In the following example, we've declared a variable named list containing a list of numbers. In its following line, we try to create another list - this time by using the list() and range() functions:
list = [1, 2, 3, 4, 5, 6, 8, 9, 10]
# ⚠️ list is no longer pointing to the list function
# Next, we try to generate a sequence to add to the current list
more_items = list(range(11, 20))
# 👆 ⛔ Raises: TypeError: ‘list’ object is not callable
If you run the above code, Python will complain with a "TypeError: 'list' object is not callable" error because we've already assigned the list name to the first list object.
We have two ways to fix the issue:
- Rename the variable
list - Explicitly access the
list()function from the builtins module (__bultins__.list)
The second approach isn't recommended unless you're developing a module. For instance, if you want to implement an open() function that wraps the built-in open():
# Custom open() function using the built-in open() internally
def open(filename):
# ...
__builtins__.open(filename, 'w', opener=opener)
# ...
In almost every other case, you should always avoid naming your variables as existing functions and methods. But if you've done so, renaming the variable would solve the issue.
So the above example could be fixed like this:
items = [1, 2, 3, 4, 5, 6, 8, 9, 10]
# Next, we try to generate a sequence to add to the current list
more_items = list(range(11, 20))
This issue is common with function names you're more likely to use as variable names. Functions such as vars, locals, list, all, or even user-defined functions.
In the following example, we declare a variable named all containing a list of items. At some point, we call all() to check if all the elements in the list (also named all) are True:
all = [1, 3, 4, True, 'hey there', 1]
# ⚠️ all is no longer pointing to the built-in function all()
# Checking if every element in all is True:
print(all(all))
# 👆 ⛔ Raises TypeError: 'list' object is not callable
Obviously, we get the TypeError because the built-in function all() is now shadowed by the new value of the all variable.
To fix the issue, we choose a different name for our variable:
items = [1, 3, 4, True, 'hey there', 1]
# Checking if every element in all is True:
print(all(items))
# Output: True
⚠️ Long story short, you should never use a function name (built-in or user-defined) for your variables!
Overriding functions (and calling them later on) is the most common cause of the "TypeError: 'list' object is not callable" error. It's similar to calling integer numbers as if they're callables.
Now, let's get to the less common mistakes that lead to this error.
Indexing a list by parenthesis rather than square brackets: Another common mistake is when you index a list by () instead of []. Based on Python semantics, the interpreter will see any identifier followed by a () as a function call. And since the parenthesis follows a list object, it's like you're trying to call a list.
As a result, you'll get the "TypeError: ‘list’ object is not callable" error.
items = [1, 2, 3, 4, 5, 6]
print(items(2))
# 👆 ⛔ Raises TypeError: 'list' object is not callable
This is how you're supposed to access a list item:
items = [1, 2, 3, 4, 5, 6]
print(items[2])
# Output: 3
Calling a method that's also the name of a property: When you define a property in a class constructor, it'll shadow any other attribute of the same name.
class Book:
def __init__(self, title, authors):
self.title = title
self.authors = authors
def authors(self):
return self.authors
book = Book('The Pragmatic Programmer', ['David Thomas', 'Andrew Hunt'])
print(book.authors())
# 👆 ⛔ Raises TypeError: 'list' object is not callable
In the above example, since we have a property named authors, the method authors() is shadowed. As a result, any reference to authors will return the property authors, returning a list object. And if you call this list object value like a function, you'll get the "TypeError: ‘list’ object is not callable" error.
The name get_authors sounds like a safer and more readable alternative:
class Book:
def __init__(self, title, authors):
self.title = title
self.authors = authors
def get_authors(self):
return self.authors
book = Book('The Pragmatic Programmer', ['David Thomas', 'Andrew Hunt'])
print(book.get_authors())
# Output: ['David Thomas', 'Andrew Hunt']
Calling a method decorated with @property decorator: The @property decorator turns a method into a “getter” for a read-only attribute of the same name. You need to access a getter method without parenthesis, otherwise you'll get a TypeError.
class Book:
def __init__(self, title, authors):
self._title = title
self._authors = authors
@property
def authors(self):
"""Get the authors' names"""
return self._authors
book = Book('The Pragmatic Programmer', ['David Thomas', 'Andrew Hunt'])
print(book.authors())
# 👆 ⛔ Raises TypeError: 'list' object is not callable
To fix it, you need to access the getter method without the parentheses:
book = Book('The Pragmatic Programmer', ['David Thomas', 'Andrew Hunt'])
print(book.authors)
# Output: ['David Thomas', 'Andrew Hunt']
Problem solved!
Alright, I think it does it! I hope this quick guide helped you fix your problem.
Thanks for reading.
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This content originally appeared on DEV Community 👩💻👨💻 and was authored by Reza Lavarian
Reza Lavarian | Sciencx (2023-02-03T13:36:46+00:00) How to fix “‘list’ object is not callable” in Python. Retrieved from https://www.scien.cx/2023/02/03/how-to-fix-list-object-is-not-callable-in-python/
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