Method object is not subscriptable ошибка

When calling a method in Python, you have to use parentheses (). If you use square brackets [], you will raise the error “TypeError: ‘method’ object is not subscriptable”.

This tutorial will describe in detail what the error means. We will explore an example scenario that raises the error and learn how to solve it.

TypeError: ‘method’ object is not subscriptable

TypeErrror occurs when you attempt to perform an illegal operation for a particular data type. The part “‘method’ object is not subscriptable” tells us that method is not a subscriptable object. Subscriptable objects have a __getitem__ method, and we can use __getitem__ to retrieve individual items from a collection of objects contained by a subscriptable object. Examples of subscriptable objects are lists, dictionaries and tuples. We use square bracket syntax to access items in a subscriptable object. Because methods are not subscriptable, we cannot use square syntax to access the items in a method or call a method.

Methods are not the only non-subscriptable object. Other common “not subscriptable” errors are:

• “TypeError: ‘float’ object is not subscriptable“,
• “TypeError: ‘int’ object is not subscriptable“
• “TypeError: ‘builtin_function_or_method’ object is not subscriptable“
• “TypeError: ‘function’ object is not subscriptable“

Let’s look at an example of retrieving the first element of a list using the square bracket syntax

pizzas = ["margherita", "pepperoni", "four cheeses", "ham and pineapple"]
print(pizzas[0])

The code returns:

margherita

which is the pizza at index position 0. Let’s look at an example of calling a method using square brackets.

Example: Calling A Method With Square Brackets

Let’s create a program that stores fundamental particles as objects. The Particle class will tell us the mass of a particle and its charge. Let’s create a class for particles.

class Particle:

         def __init__(self, name, mass):

             self.name = name

             self.mass = mass

         def is_mass(self, compare_mass):

             if compare_mass != self.mass:

                 print(f'The {self.name} mass is not equal to {compare_mass} MeV, it is {self.mass} MeV')

             else:

                 print(f'The {self.name} mass is equal to {compare_mass} MeV')

The Particle class has two methods, one to define the structure of the Particle object and another to check if the mass of the particle is equal to a particular value. This class could be useful for someone studying Physics and particle masses for calculations.

Let’s create a muon object with the Particle class. The mass is in MeV and to one decimal place.

muon = Particle("muon", 105.7)

The muon variable is an object with the name muon and mass value 105.7. Let’s see what happens when we call the is_mass() method with square brackets and input a mass value.

muon.is_mass[105.7]

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Input In [18], in <cell line: 1>()
----> 1 muon.is_mass[105.7]

TypeError: 'method' object is not subscriptable

We raise the TypeError because of the square brackets used to call the is_mass() method. The square brackets are only suitable for accessing items from a list, a subscriptable object. Methods are not subscriptable; we cannot use square brackets when calling this method.

Solution

We replace the square brackets with the round brackets ().

muon = Particle("muon", 105.7)

Let’s call the is_mass method with the correct brackets.

muon.is_mass(105.7)

muon.is_mass(0.51)

The muon mass is equal to 105.7 MeV

The muon mass is not equal to 0.51 MeV, it is 105.7 MeV

The code tells us the mass is equal to 105.7 MeV but is not equal to the mass of the electron 0.51 MeV.

To learn more about correct class object instantiation and calling methods in Python go to the article titled “How to Solve Python missing 1 required positional argument: ‘self’“.

Summary

Congratulations on reading to the end of this tutorial! The error “TypeError: ‘method’ object is not subscriptable” occurs when you use square brackets to call a method. Methods are not subscriptable objects and therefore cannot be accessed like a list with square brackets. To solve this error, replace the square brackets with the round brackets after the method’s name when you are calling it.

To learn more about Python for data science and machine learning, go to the online courses page on Python for the best courses available!

Have fun and happy researching!

Arguments in Python methods must be specified within parentheses. This is because functions and methods both use parentheses to tell if they are being called. If you use square brackets to call a method, you’ll encounter an “TypeError: ‘method’ object is not subscriptable” error.

In this guide, we discuss what this error means and why you may encounter it. We walk through an example of this error to help you develop a solution.

TypeError: ‘method’ object is not subscriptable

Subscriptable objects are objects with a __getitem__ method. These are data types such as lists, dictionaries, and tuples. The __getitem__ method allows the Python interpreter to retrieve an individual item from a collection.

Not all objects are subscriptable. Methods, for instance, are not. This is because they do not implement the __getitem__ method. This means you cannot use square bracket syntax to access the items in a method or to call a method.

Consider the following code snippet:

cheeses = ["Edam", "Stilton", "English Cheddar", "Parmesan"]
print(cheeses[0])

This code returns “Edam”, the cheese at the index position 0. We cannot use square brackets to call a function or a method because functions and methods are not subscriptable objects.

An Example Scenario

Here, we build a program that stores cheeses in objects. The “Cheese” class that we use to define a cheese will have a method that lets us check whether a cheese is from a particular country of origin.

Start by defining a class for our cheeses. We call this class Cheese:

class Cheese:
	def __init__(self, name, origin):
		self.name = name
		self.origin = origin

	def get_country(self, to_compare):
		if to_compare == self.origin:
			print("{} is from {}.".format(self.name, self.origin))
		else:
			print("{} is not from {}. It is from {}.".format(self.name, to_compare, self.origin))

Our class contains two methods. The first method defines the structure of the Cheese object. The second lets us check whether the country of origin of a cheese is equal to a particular value. 

Next, we create an object from our Cheese class:

edam = Cheese("Edam", "Netherlands")

The variable “edam” is an object. The name associated with the cheese is Edam and its country of origin is the Netherlands.

Next, let’s call our get_country() method:

edam.get_country["Germany"]

This code executes the get_country() method from the Cheese class. The get_country() method checks whether the value of “origin” in our “edam” object is equal to “Germany”.

Run our code and see what happens:

Traceback (most recent call last):
  File "main.py", line 14, in <module>
	edam.get_country["Germany"]
TypeError: 'method' object is not subscriptable

An error occurs in our code.

The Solution

Let’s analyze the line of code that the Python debugger has identified as erroneous:

edam.get_country["Germany"]

In this line of code, we use square brackets to call the get_country() method. This is not acceptable syntax because square brackets are used to access items from a list. Because functions and objects are not subscriptable, we cannot use square brackets to call them.

To solve this error, we must replace the square brackets with curly brackets:

edam.get_country("Germany")

Let’s run our code and see what happens:

Edam is not from Germany. It is from Netherlands.

Our code successfully executes. Let’s try to check whether Edam is from “Netherlands” to make sure our function works in all cases, whether or not the value we specify is equal to the cheese’s origin country:

edam.get_country("Netherlands")

Our code returns:

Edam is from Netherlands.

Our code works if the value we specify is equal to the country of origin of a cheese.

Conclusion

The “TypeError: ‘method’ object is not subscriptable” error is raised when you use square brackets to call a method inside a class. To solve this error, make sure that you only call methods of a class using curly brackets after the name of the method you want to call.

Now you’re ready to solve this common Python error like a professional coder!

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