type object is not subscriptable

Estimated reading time: 2 minutes

I was recently working on our last blog post how to reverse a string in python and I came across this error.

The thought passed me what does it mean and how can I fix it?

So what does the error actually mean?

Essentially it means that , you are trying to access a type of an object, that has a property of “type”.

What is property of type? Well it is :

  • int()
  • str()
  • tuple()
  • dict()

The above alllow you to change your data to these data types, so the data contained within them can be further manipulated.

In essence you are trying to use a type in the wrong way and in the wrong place in your code.

By calling it , it will throw this error, and they should be avoided, as a it is a built in function.

Lets take an example of how we can replicate this error and fix it

name1 = "joe"
emptylist =[]
strlength = len(name1)
while strlength > 0:
    emptylist += str[ strlength -1 ]
    strlength = strlength - 1

In the above code all appears well, but in line 5 the “str” before the [ is the problem. The code automatically looks to call this function.

The simple answer to fixing this is to rename it to name1 as follows:

name1 = "joe"
emptylist =[]
strlength = len(name1)
while strlength > 0:
    emptylist += name1[ strlength -1 ]
    strlength = strlength - 1

which gives you the following error free output:

Result with no error: ['e', 'o', 'j']

In summary and what not to do

So it is clear that referencing types as a string variable should be avoided, and keep your code clean from this perspective.

This would also apply to any reserved words in Python as well.

What are the reserved keywords in Python

What are python reserved keywords?

When coding in the Python language there are particular python reserved words that the system uses, which cannot be accessed as a variable or a function as the computer program uses them to perform specific tasks.

When you try to use them, the system will block it and throws out an error. Running the below code in Python

import keyword
keywordlist = keyword.kwlist

Produces the below keyword values
['False', 'None', 'True', 'and', 'as', 'assert', 'async', 'await', 'break', 'class', 'continue', 'def', 'del',
'elif', 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'nonlocal',
'not', 'or', 'pass', 'raise', 'return', 'try', 'while', 'with', 'yield']

When writing your code, it is important to follow the following guidelines:

(A) Research the keywords first for the language you are writing in.

(B) Ensure that your programming language highlights keywords when used, so you can fix the issue.

(C) Setup your computer program in debug mode to highlight keywords use.

With some programs running into thousands of lines of code, with additional functions and variables, it can become harder to spot the problem, so good rigour in the initial stages of coding will help down the road any issues that you may find that need to fixed.

This code was run in Python version 3.8