Why am I seeing "TypeError: string indices must be integers"? Why am I seeing "TypeError: string indices must be integers"? python python

Why am I seeing "TypeError: string indices must be integers"?


The variable item is a string. An index looks like this:

>>> mystring = 'helloworld'>>> print mystring[0]'h'

The above example uses the 0 index of the string to refer to the first character.

Strings can't have string indices (like dictionaries can). So this won't work:

>>> mystring = 'helloworld'>>> print mystring['stringindex']TypeError: string indices must be integers


item is most likely a string in your code; the string indices are the ones in the square brackets, e.g., gravatar_id. So I'd first check your data variable to see what you received there; I guess that data is a list of strings (or at least a list containing at least one string) while it should be a list of dictionaries.


TypeError for Slice Notation str[a:b]


Short Answer

Use a colon : instead of a comma in between the two indices a and b in str[a:b] (e.g. instead of my_string[0,5] write my_string[0:5]).


Long Answer

When working with strings and slice notation (a common sequence operation), it can happen that a TypeError is raised, pointing out that the indices must be integers, even if they obviously are.

Example

>>> my_string = "hello world">>> my_string[0,5]TypeError: string indices must be integers

We obviously passed two integers for the indices to the slice notation, right? So what is the problem here?

This error can be very frustrating - especially at the beginning of learning Python - because the error message is a little bit misleading.

Explanation

We implicitly passed a tuple of two integers (0 and 5) to the slice notation when we called my_string[0,5] because 0,5 (even without the parentheses) evaluates to the same tuple as (0,5) would do.

A comma , is actually enough for Python to evaluate something as a tuple:

>>> my_variable = 0,>>> type(my_variable)<class 'tuple'>

So what we did there, this time explicitly:

>>> my_string = "hello world">>> my_tuple = 0, 5>>> my_string[my_tuple]TypeError: string indices must be integers

Now, at least, the error message makes sense.

Solution

We need to replace the comma , with a colon : to separate the two integers correctly:

>>> my_string = "hello world">>> my_string[0:5]'hello'

A clearer and more helpful error message could have been something like:

TypeError: string indices must be integers (not tuple)

A good error message shows the user directly what they did wrong and it would have been more obvious how to solve the problem.

[So the next time when you find yourself responsible for writing an error description message, think of this example and add the reason or other useful information to error message to let you and maybe other people understand what went wrong.]

Lessons learned

  • slice notation uses colons : to separate its indices (and step range, e.g. str[from:to:step])
  • tuples are defined by commas , (e.g. t = 1,)
  • add some information to error messages for users to understand what went wrong

Cheers and happy programming
winklerrr


[I know this question was already answered and this wasn't exactly the question the thread starter asked, but I came here because of the above problem which leads to the same error message. At least it took me quite some time to find that little typo.

So I hope that this will help someone else who stumbled upon the same error and saves them some time finding that tiny mistake.]


matomo