What does it mean if a Python object is subscriptable or not

Question

Which types of objects fall into the domain of  subscriptable

User · Answer

The meaning of subscript in computing is: "a symbol (notionally written as a subscript but in practice usually not) used in a program, alone or with others, to specify one of the elements of an array."

Now, in the simple example given by @user2194711 we can see that the appending element is not able to be a part of the list because of two reasons:-

1) We are not really calling the method append; because it needs () to call it.

2) The error is indicating that the function or method is not subscriptable; means they are not indexable like a list or sequence.

Now see this:-

>>> var = "myString"
>>> def foo(): return 0
... 
>>> var[3]
't'
>>> foo[3]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'function' object is not subscriptable

That means there are no subscripts or say elements in function like they occur in sequences; and we cannot access them like we do, with the help of [].

Also; as mipadi said in his answer; It basically means that the object implements the __getitem__() method. (if it is subscriptable). Thus the error produced:

arr.append["HI"]

TypeError: 'builtin_function_or_method' object is not subscriptable

User · Answer

It basically means that the object implements the   getitem     method  In other words  it describes objects that are  containers   meaning they contain other objects  This includes strings  lists  tuples  and dictionaries

User · Answer

It basically means that the object implements the   getitem     method  In other words  it describes objects that are  containers   meaning they contain other objects  This includes strings  lists  tuples  and dictionaries

User · Answer

A scriptable object is an object that records the operations done to it and it can store them as a  script  which can be replayed   For example  see  Application Scripting Framework  Now  if Alistair didn t know what he asked and really meant  subscriptable  objects  as edited by others   then  as mipadi also answered  this is the correct one   A subscriptable object is any object that implements the   getitem   special method  think lists  dictionaries

User · Answer

As a corollary to the earlier answers here  very often this is a sign that you think you have a list  or dict  or other subscriptable object  when you do not   For example  let s say you have a function which should return a list   def gimme things        if something happens            return   all    the    things     Now when you call that function  and something happens   for some reason does not return a True value  what happens  The if fails  and so you fall through  gimme things doesn t explicitly return anything  -- so then in fact  it will implicitly return None  Then this code   things   gimme things   print  My first thing is  0   format things 0      will fail with  NoneType object is not subscriptable  because  well  things is None and so you are trying to do None 0  which doesn t make sense because     what the error message says   There are two ways to fix this bug in your code -- the first is to avoid the error by checking that things is in fact valid before attempting to use it   things   gimme things   if things      print  My first thing is  0   format things 0    else      print  No things      or raise an error  or do nothing  or       or equivalently trap the TypeError exception   things   gimme things   try      print  My first thing is  0   format things 0    except TypeError      print  No things      or raise an error  or do nothing  or       Another is to redesign gimme things so that you make sure it always returns a list  In this case  that s probably the simpler design because it means if there are many places where you have a similar bug  they can be kept simple and idiomatic   def gimme things        if something happens            return   all    the    things       else     make sure we always return a list  no matter what          logging info  Something didn t happen  return empty list           return      Of course  what you put in the else  branch depends on your use case  Perhaps you should raise an exception when something happens   fails  to make it more obvious and explicit where something actually went wrong   Adding exceptions to your own code is an important way to let yourself know exactly what s up when something fails    Notice also how this latter fix still doesn t completely fix the bug -- it prevents you from attempting to subscript None but things 0  is still an IndexError when things is an empty list  If you have a try you can do except  TypeError  IndexError  to trap it  too

User · Answer

Off the top of my head  the following are the only built-ins that are subscriptable   string    foobar  3      b  tuple     1 2 3 4  3     4 list      1 2 3 4  3     4 dict       a  1   b  2   c  3   c      3   But mipadi s answer is correct - any class that implements   getitem   is subscriptable

User · Answer

A scriptable object is an object that records the operations done to it and it can store them as a  script  which can be replayed   For example  see  Application Scripting Framework  Now  if Alistair didn t know what he asked and really meant  subscriptable  objects  as edited by others   then  as mipadi also answered  this is the correct one   A subscriptable object is any object that implements the   getitem   special method  think lists  dictionaries

User · Answer

I had this same issue  I was doing  arr      arr append  HI     So using   was causing error  It should be arr append  HI

User · Answer

It basically means that the object implements the   getitem     method  In other words  it describes objects that are  containers   meaning they contain other objects  This includes strings  lists  tuples  and dictionaries

User · Answer

I had this same issue  I was doing  arr      arr append  HI     So using   was causing error  It should be arr append  HI

User · Answer

A scriptable object is an object that records the operations done to it and it can store them as a  script  which can be replayed   For example  see  Application Scripting Framework  Now  if Alistair didn t know what he asked and really meant  subscriptable  objects  as edited by others   then  as mipadi also answered  this is the correct one   A subscriptable object is any object that implements the   getitem   special method  think lists  dictionaries

User · Answer

It basically means that the object implements the   getitem     method  In other words  it describes objects that are  containers   meaning they contain other objects  This includes strings  lists  tuples  and dictionaries

User · Answer

A scriptable object is an object that records the operations done to it and it can store them as a  script  which can be replayed   For example  see  Application Scripting Framework  Now  if Alistair didn t know what he asked and really meant  subscriptable  objects  as edited by others   then  as mipadi also answered  this is the correct one   A subscriptable object is any object that implements the   getitem   special method  think lists  dictionaries

User · Answer

Off the top of my head  the following are the only built-ins that are subscriptable   string    foobar  3      b  tuple     1 2 3 4  3     4 list      1 2 3 4  3     4 dict       a  1   b  2   c  3   c      3   But mipadi s answer is correct - any class that implements   getitem   is subscriptable

User · Answer

Off the top of my head  the following are the only built-ins that are subscriptable   string    foobar  3      b  tuple     1 2 3 4  3     4 list      1 2 3 4  3     4 dict       a  1   b  2   c  3   c      3   But mipadi s answer is correct - any class that implements   getitem   is subscriptable

User · Answer

Off the top of my head  the following are the only built-ins that are subscriptable   string    foobar  3      b  tuple     1 2 3 4  3     4 list      1 2 3 4  3     4 dict       a  1   b  2   c  3   c      3   But mipadi s answer is correct - any class that implements   getitem   is subscriptable

User · Answer

As a corollary to the earlier answers here  very often this is a sign that you think you have a list  or dict  or other subscriptable object  when you do not   For example  let s say you have a function which should return a list   def gimme things        if something happens            return   all    the    things     Now when you call that function  and something happens   for some reason does not return a True value  what happens  The if fails  and so you fall through  gimme things doesn t explicitly return anything  -- so then in fact  it will implicitly return None  Then this code   things   gimme things   print  My first thing is  0   format things 0      will fail with  NoneType object is not subscriptable  because  well  things is None and so you are trying to do None 0  which doesn t make sense because     what the error message says   There are two ways to fix this bug in your code -- the first is to avoid the error by checking that things is in fact valid before attempting to use it   things   gimme things   if things      print  My first thing is  0   format things 0    else      print  No things      or raise an error  or do nothing  or       or equivalently trap the TypeError exception   things   gimme things   try      print  My first thing is  0   format things 0    except TypeError      print  No things      or raise an error  or do nothing  or       Another is to redesign gimme things so that you make sure it always returns a list  In this case  that s probably the simpler design because it means if there are many places where you have a similar bug  they can be kept simple and idiomatic   def gimme things        if something happens            return   all    the    things       else     make sure we always return a list  no matter what          logging info  Something didn t happen  return empty list           return      Of course  what you put in the else  branch depends on your use case  Perhaps you should raise an exception when something happens   fails  to make it more obvious and explicit where something actually went wrong   Adding exceptions to your own code is an important way to let yourself know exactly what s up when something fails    Notice also how this latter fix still doesn t completely fix the bug -- it prevents you from attempting to subscript None but things 0  is still an IndexError when things is an empty list  If you have a try you can do except  TypeError  IndexError  to trap it  too

User · Answer

The meaning of subscript in computing is: "a symbol (notionally written as a subscript but in practice usually not) used in a program, alone or with others, to specify one of the elements of an array."

Now, in the simple example given by @user2194711 we can see that the appending element is not able to be a part of the list because of two reasons:-

1) We are not really calling the method append; because it needs () to call it.

2) The error is indicating that the function or method is not subscriptable; means they are not indexable like a list or sequence.

Now see this:-

>>> var = "myString"
>>> def foo(): return 0
... 
>>> var[3]
't'
>>> foo[3]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'function' object is not subscriptable

That means there are no subscripts or say elements in function like they occur in sequences; and we cannot access them like we do, with the help of [].

Also; as mipadi said in his answer; It basically means that the object implements the __getitem__() method. (if it is subscriptable). Thus the error produced:

arr.append["HI"]

TypeError: 'builtin_function_or_method' object is not subscriptable

[python] What does it mean if a Python object is "subscriptable" or not?

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