Overview
Example errors:
TypeError: object is not subscriptable
Specific examples:
TypeError: 'type' object is not subscriptableTypeError: 'function' object is not subscriptable
Traceback (most recent call last):
File "afile.py", line , in aMethod
map[value]
TypeError: 'type' object is not subscriptable
This problem is caused by trying to access an object that cannot be indexed as though it can be accessed via an index.
For example, in the above error, the code is trying to access map[value] but map is already a built-in type that doesn’t support accessing indexes.
You would get a similar error if you tried to call print[42], because print is a built-in function.
Initial Steps Overview
Detailed Steps
1) Check for built-in words in the given line
In the above error, we see Python shows the line
map[value]
This is saying that the part just before [value] can not be subscripted (or indexed). In this particular instance, the problem is that the word map is already a builtin identifier used by Python and it has not been redefined by us to contain a type that subscripts.
You can see a full list of built-in identifiers via the following code:
# Python 3.0
import builtins
dir(builtins)
# For Python 2.0
import __builtin__
dir(__builtin__)
2) Check for instances of the following reserved words
It may also be that you are trying to subscript a keyword that is reserved by Python True, False or None
>>> True[0]
<stdin>:1: SyntaxWarning: 'bool' object is not subscriptable; perhaps you missed a comma?
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'bool' object is not subscriptable
3) Check you are not trying to access elements of a function
Check you are not trying to access an index on a method instead of the results of calling a method.
txt = 'Hello World!'
# Incorrectly getting the first word
>>> txt.split[0]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'builtin_function_or_method' object is not subscriptable
# The correct way
>>> txt.split()[0]
'Hello'
You will get a similar error for functions/methods you have defined yourself:
def foo():
return ['Hello', 'World']
# Incorrectly getting the first word
>>> foo[0]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: 'function' object is not subscriptable
# The correct way
>>> foo()[0]
'Hello'
Solutions List
B) Don’t shadow built-in names
Solutions Detail
A) Initialize the value
Make sure that you are initializing the array before you try to access its index.
map = ['Hello']
print(map[0])
Hello
B) Don’t shadow built-in names
It is generally not a great idea to shadow a language’s built-in names as shown in the above solution as this can confuse others reading your code who expect map to be the builtin map and not your version.
If we hadn’t used an already taken name we would have also got a much more clear error from Python, such as:
>>> foo[0]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'foo' is not defined
But don’t just take our word for it: see here
