How to Fix TypeError: list indices must be integers or slices, not tuple in Python

When you're working in Python, especially with lists and tuples, you might come across this error:

BASH
TypeError: list indices must be integers or slices, not tuple

This error is caused by the fact that you're trying to access a list element by a tuple.

In this post, we'll look and some example code that causes this error and how to fix it.

How to fix TypeError: list indices must be integers or slices, not tuple

Before we learn how to fix it, let's look at some example code that causes this error:

PYTHON
locations = [
    ["New York", "USA"]
    ["Paris", "France"]
]

london = ["London", "UK"]

locations.append(london)

print(locations)

Depending on your compiler, you might even already get the solution to this problem:

BASH
<string>:2: SyntaxWarning: list indices must be integers or slices, not tuple; perhaps you missed a comma?
Traceback (most recent call last):
File "<string>", line 2, in <module>
TypeError: list indices must be integers or slices, not tuple

It says it on the first line of this error, that perhaps you missed a comma, and indeed we did.

By defining locations without a comma, we're creating a list of lists, instead of a list of tuples.

That distinction is the root of the problem.

All we need to do is add a comma so that the compiler understands that this is a list of tuples:

PYTHON
locations = [
    ["New York", "USA"],
    ["Paris", "France"]
]

london = ["London", "UK"]

locations.append(london)

print(locations)

As expected, this now works without errors.

BASH
[['New York', 'USA'], ['Paris', 'France'], ['London', 'UK']]

Conclusion

In this post, we learned how to fix the problem of TypeError: list indices must be integers or slices, not tuple.

Simply ensure that you are using a list of tuples, instead of a list of lists, which can be done by adding a comma to separate the different tuples.

Thanks for reading!

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