Fix TypeError: list indices must be integers or slices, not str

If you’re a Python Developer or maybe a Beginner learning Development in Python you might have encountered this typeerror Error: list indices must be integers or slices, not str. After this error, you might have googled this error or maybe changed something in the code and it worked out, but you still don’t know what was the error or the reason behind this error.

Maybe if you’re reading this article there’s a high chance that you still are facing this issue, and you’re here for the solution. In this article, we’ll break down this typeerror and solve this issue from ground zero.

Why did this Error occur??

This typeerror occurs whenever we use Strings instead of indices or slices for list Indexing. Let’s take a look at the code below

#  index =   0   1   2   3   4   5   6   7   8   9
Our_list = [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ]
Code language: Python (python)

In the above code, we can see that to access for example element 5 we have to use Our_list[4]. We’ve to provide its index number.

    #  index =   0   1   2   3   4   5   6   7   8   9
    Our_list = [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ]

    print(Our_list[4])
Code language: Python (python)

But what if we’ve given the index number as a String

print(Our_list['4'])
Code language: Python (python)

In this case, we’ll see the Error named Fix TypeError: list indices must be integers or slices, not str.

List Indexing in python refers to giving the start point, endpoint, and step size to get the sub-list of the original list. Let’s look at the code below to understand List Indexing in a better way.

Our_list = [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ]

print(Our_list[2:7]) #gives us output -> [3, 4, 5, 6, 7]

print(Our_list[2:7:2]) #gives us output -> [3, 5, 7]
Code language: Python (python)

From the above code, we can see that list Indexing can help us in many ways.

In the first print statement, we got a sub-list of 5 Integers from index 2 to index 6 ( being the last given endpoint excluded ).

In the second print statement, we step forward and included a step value too which enables python to move forward with the step value.

As a Python Developer, you might face this problem a lot of times obviously if the slicing indexes are not correctly managed. But here in this article, we’ll see the top 3 uses where you might face this error while working with Lists in Python.

Common Cases when this Error occurs

The Three cases are listed below:-

• Unconverted Strings
• Treating Lists as Dictionaries
• Using List Values for Indexing

UnConverted Strings

Unconverted Strings mean that you’re trying to access a particular element of a string but you still giving the indexes as Strings. Let’s look at the code below

List_Of_Games = ["CyberPunk 2077", "Call Of Duty: Warzone", "Counter Strike: Global Offensive", "Valorant", "Assassin's Creed Valhalla"]

for i in List_Of_Games:
    print(f"{List_Of_Games.index(i)+1}: {i}")

choice = input("Which game you wanna play with me??")

print(List_Of_Games[choice])
Code language: Python (python)

By seeing the above code, you might think about what the error is here. It should be working fine. But, upon looking closely you might get to know that, we’re getting input as a String in the choice variable.

For List Indexing, it always has to be Integer not a String to perform List Indexing. To rectify this error, you might have to typecast the choice variable to Integer.

Solution

To solve this issue, we’ve to explicitly typecast the input from the user, and based on that input we can provide the indexes to the list.

List_Of_Games = ["CyberPunk 2077", "Call Of Duty: Warzone", "Counter Strike: Global Offensive", "Valorant", "Assassin's Creed Valhalla"]

for i in List_Of_Games:
    print(f"{List_Of_Games.index(i)+1}: {i}")

try:
    choice = int(input("Which game you wanna play with me??"))
except:
    print("Wrong Input Entered!! Quitting the Program")
    exit()

print(List_Of_Games[choice])
Code language: Python (python)

Upon Typecasting the choice variable we’ll only receive the Integer value in the choice variable and be able to provide an Index to List_Of_Games in Integer rather than of String.

Treating Lists as Dictionaries

Based on the previous Code we saw let’s try to build a List with the usernames and try to print the username when a certain Game matches with the hardcoded Game.

List_Of_Games = [
    {
        "Name":"CyberPunk 2077",
        "Username": "iDontPlayCyberPunk"
    },
    {
        "Name": "Call Of Duty: Warzone",
        "Username": "minininja"
    },
    {
        "Name": "Counter Strike: Global Offensive",
        "Username": "the_brave_gamer"
    },
    {
        "Name": "Valorant",
        "Username": "thebravegamer#askmeforusername"
    },
    {
        "Name": "Assassin's Creed Valhalla",
        "Username": "CompetetiveNahiKhelta"
    },
]
if List_Of_Games["Name"] == "CyberPunk 2077":
    print("It's full of bugs but still I Play Pirated Game.")
Code language: Python (python)

In the above code, we can see that we’re trying to access the Names of the Games but we’re giving indices as it’s a dictionary. We’re trying to access the dictionary which is inside the list. To make the program executable we’ve to give the proper index of the dictionary within the list.

Solution

List_Of_Games = [
    {
        "Name":"CyberPunk 2077",
        "Username": "iDontPlayCyberPunk"
    },
    {
        "Name": "Call Of Duty: Warzone",
        "Username": "minininja"
    },
    {
        "Name": "Counter Strike: Global Offensive",
        "Username": "the_brave_gamer"
    },
    {
        "Name": "Valorant",
        "Username": "thebravegamer#askmeforusername"
    },
    {
        "Name": "Assassin's Creed Valhalla",
        "Username": "CompetetiveNahiKhelta"
    },
]
for i in range(len(List_Of_Games)):
    if List_Of_Games[i]["Name"] == "CyberPunk 2077":
        print("It's full of bugs but still I Play Pirated Game.")
Code language: Python (python)

In the above Solution, we’re trying to iterate over all the list elements, and with that, we’re also iterating over the dictionary that’s available on the first Index only.

So our new script works because from the for loop we can iterate over the list elements and then we can check for dictionary within the list.

Using List Values for Indexing

This Error can also occur when you’re trying to put the list elements as the index for another or the list itself. Let’s take an example where you’re trying to give the element of one list as the index for another list.

Number_Of_Games = [ "1", "2", "3", "4", "5" ]
List_Of_Games = ["CyberPunk 2077", "Call Of Duty: Warzone", "Counter Strike: Global Offensive", "Valorant", "Assassin's Creed Valhalla"]

print(List_Of_Games[Number_Of_Games[3]])
Code language: Python (python)

In the above Code, we saw that List_Of_Games will have an index of 3rd elements from Number_Of_Games, due to the element being a type of string so it’ll always be giving us an Error of TypeError: list indices must be integers or slices, not str.

Solution

So to get an output from this We have two options to rectify this code

• either make all the elements in Number_Of_Games into Integer
• or directly give input to List_Of_Games.

Approach 1

Number_Of_Games = [ 1, 2, 3, 4, 5 ]
List_Of_Games = ["CyberPunk 2077", "Call Of Duty: Warzone", "Counter Strike: Global Offensive", "Valorant", "Assassin's Creed Valhalla"]

print(List_Of_Games[Number_Of_Games[3]])
Code language: Python (python)

By Converting all the elements of Number_Of_Games to Integer we ultimately gave the input to List_Of_Games in an Integer type, resulting in us Valorant.

Approach 2

List_Of_Games = ["CyberPunk 2077", "Call Of Duty: Warzone", "Counter Strike: Global Offensive", "Valorant", "Assassin's Creed Valhalla"]

print(List_Of_Games[3])
Code language: Python (python)

In this approach, we’re giving input directly, which is also an optimized way of operating with lists unless there is a need. As we can see in the List_Of_Games the list could’ve been overridden.

Approach 3

Number_Of_Games = [ 1, 2, 3, 4, 5 ]
List_Of_Games = ["CyberPunk 2077", "Call Of Duty: Warzone", "Counter Strike: Global Offensive", "Valorant", "Assassin's Creed Valhalla"]

print(List_Of_Games[int(Number_Of_Games[3])])
Code language: Python (python)

In this approach, we can just typecast the element we’re getting from the first list before providing it as input to the second list. This saves a lot of time which we’re exerting in the above both approaches.

Summary

This error generally occurs whenever we try to access the list using indexes but give strings instead of integers or slices in place of either the start point, end point, or step value. The most common solution to this problem is explicitly typecasting the index to an integer. This helps the developer override the necessity to either convert the other list to an integer or hardcoding the index to the list.

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Thanks for reading
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