Problem Formulation Consider the following minimal example where a TypeError: ‘float’ object is not subscriptable occurs: This yields the following output: Solution Overview Python raises the TypeError: ‘float’ object is not subscriptable if you use indexing or slicing with the square bracket notation on a float variable that is not indexable. However, the float class … Read more
Do you encounter the following error message? TypeError: NoneType is not subscriptable You’re not alone! This short tutorial will show you why this error occurs, how to fix it, and how to never make the same mistake again. So, let’s get started! Summary Python raises the TypeError: NoneType is not subscriptable if you try to … Read more
Python __version__ Attribute Python contains many “Magic Methods/Attributes”. One of these is __version__ commonly called “Dunder version” because of the double underscore before and after version. In this article, I will briefly look at what a Dunder Method/Attribute is and talk about __version__. What Does a Dunder Method/Attribute Do? Dunder Methods/Attributes, also called “Magic Methods” … Read more
The TypeError: unhashable type: ‘list’ usually occurs when you try to use a list object as a set element or dictionary key and Python internally passes the unhashable list into the hash() function. But as lists are mutable objects, they do not have a fixed hash value. The easiest way to fix this error is … Read more
object.__aiter__(self) object.__anext__(self) 💡 Summary: Python’s __aiter__() and __anext__() methods are used to implement an asynchronous for loop (keywords: async for). In contrast to a normal (synchronous) for loop, an asynchronous for loop iterates over an asynchronous source. __aiter__() returns an asynchronous iterator object (in many cases it’s simply a reference to itself: return self) __anext__() … Read more
object.__aexit__(self, exc_type, exc_val, exc_tb) 💡 Summary: Python’s __aexit__() magic method is semantically similar to __exit__() but is used for asynchronous and parallel programming. Python calls the __aexit__() magic method when leaving an async with block whereas the __aenter__() method is called when entering it. An object that implements both __aenter__() and __aexit__() methods is called … Read more
object.__aenter__(self) 💡 Summary: Python’s __aenter__() magic method is semantically identical to __enter__() but is used for asynchronous and parallel programming. Python calls the __aenter__() magic method when starting an async with block whereas the __aexit__() method is called when leaving it. An object that implements both __aenter__() and __aexit__() methods is called an asynchronous context … Read more
object.__exit__(self, exc_type, exc_value, traceback) 💡 Summary: Python calls the __exit__() magic method when ending a with block whereas the __enter__() method is called at the start. An object that implements both __exit__() and __enter__() is called a context manager. By defining those methods, you can create your own context manager. We define a custom class … Read more
object.__enter__(self) 💡 Summary: Python calls the __enter__() magic method when starting a with block whereas the __exit__() method is called at the end. An object that implements both __enter__() and __exit__() methods is called a context manager. By defining those methods, you can create your own context manager. We define a custom class MySecretConnection. This … Read more
Syntax object.__format__(self, spec) The Python __format__() method implements the built-in format() function as well as the string.format() method. So, when you call format(x, spec) or string.format(spec), Python attempts to call x.__format__(spec). The return value is a string. We call this a “Dunder Method” for “Double Underscore Method” (also called “magic method”). To get a list … Read more
Python’s magic method obj.__set_name__(self, owner, name) method is created on an attribute obj when the class owner holding the attribute is created. We call this a “Dunder Method” for “Double Underscore Method” (also called “magic method”). To get a list of all dunder methods with explanation, check out our dunder cheat sheet article on this … Read more
Python’s __set__() magic method sets a given attribute on an instance of a class holding the attribute (=owner class) to a new value. When setting the attribute through the owner class, Python dynamically executes the attribute’s __set__() method to override its value on the given instance argument. For example, if you create a class Person … Read more