Type errors are a common problem for programmers. The list you’re trying to work with is unhashable, which means there’s something wrong with it. This can happen if the list has been modified in some way that Python doesn’t recognize, or if the list contains objects that Python doesn’t understand how to process. In this article, we’ll go over different ways to fix type errors and what they mean so you don’t get stuck!
Fixing a TypeError: Unhashable type
The list you’re trying to work with is unhashable, which means there’s something wrong with it. This can happen if the list has been modified in some way that Python doesn’t recognize or if the list contains objects that Python doesn’t understand how to process. In this article, we’ll go over different ways to fix type errors and what they mean so you don’t get stuck!
We use the list function or append function to create new lists. We also use it when working with data structures like tuples that are immutable.
The list can be fixed by adding an empty list at the beginning. This is known as “tacking on” and will cause Python to start scanning from the new, first item in order to find values that need fixing. Here’s one example of how we could tack on an empty list:
a = [“a”]
b.append([“b”],) # will create [‘a’, ‘b’] and not fix the type error because it does not recognize “b” as being in the list of items to process because we are slicing an empty list into our existing one at position 0.
What do these errors mean? They are telling you that the variable that they’re attempting to use is of a different data type than what we would expect it to be.
In this example, the type error is telling us that it cannot process a list because it’s of an unhashable data type. In other words, we’re trying to use something like “b” or [“a”] and Python doesn’t know how to deal with these types – specifically the list.
What can we do about it? There are a few options, but one is to append an empty list:
*b.append([“b”],) # will create [‘a’, ‘b’] and not fix the type error because it does not recognize “b” as being in the list of items to process
How do you know if this is the best solution? This is always going to be up for debate depending on what kind of work our code is doing.
However, one thing we can do is test and see what the type error is telling us:
list(b) # does this fix our problem?
TypeError: unhashable type: ‘list’ >>> False
This means that adding an empty list to b will not fix the error because Python recognizes “b” as the list, not “list”.
So what do we do? We can use a list comprehension to fix this error.
b = [a + [“b”] for _ in range(len(_) – len(a))] # now Python recognizes ‘all of these items’ and stops giving us an error
b # list of ‘a’, ‘b’
Python has recognized “b” as the list, not “list”. It stops giving us an error and now returns a list with two items.
This is by no means the only solution to this type of error – there are many solutions for different situations out there! However, this is a great one to know and use.
How to fix these errors?
type error: unhashable type >>> False
list comprehension to fix the problem. This is by no means the only solution for this kind of situation – there are many solutions out there! However, it’s a great one to know and use.
So what do we do? We can use a list comprehension to fix the problem. This is by no means the only solution for this type of situation – there are many solutions out there! However, it’s a great one to know and use.
List comprehensions can be used when you need to build lists from other lists or iterables in order:
list comprehension (range(len(my_list) + len(another_list)))
list comprehensions can be used when you need to build lists from other lists or iterables in order:
range (len(my_list) + len(another_list))
This is an example of a type error and how we would fix it using list comprehensions.
