Why is an int object not an error being caused when using the sum () function?

Question

I am trying to understand why I get an error when using the sum function in a range.

Here is the code:

data1 = range(0, 1000, 3) data2 = range(0, 1000, 5) data3 = list(set(data1 + data2)) # makes new list without duplicates total = sum(data3) # calculate sum of data3 list elements print total 

And here is the error:

 line 8, in <module> total2 = sum(data3) TypeError: 'int' object is not callable 

I found this error explanation:

In Python, a "callable" is usually a function. The message means that you are handling the number (→ int) as if it were a function ("called"), so Python does not know what to do, therefore ita> stops.

I also read that sum () can be used in lists, so I wonder what is going wrong here?

I just tried it in the IDLE module and it worked fine. However, it does not work in the python interpreter. Any ideas on how this could be?

Answer 1

You have probably redefined your function "sum" as an integer data type. Therefore, it is fair to tell you that an integer is not something that you can convey to a range.

To fix this, restart your interpreter.

 Python 2.7.3 (default, Apr 20 2012, 22:44:07) [GCC 4.6.3] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> data1 = range(0, 1000, 3) >>> data2 = range(0, 1000, 5) >>> data3 = list(set(data1 + data2)) # makes new list without duplicates >>> total = sum(data3) # calculate sum of data3 list elements >>> print total 233168 

If you obscure the built-in sum , you may get the error message that you see

 >>> sum = 0 >>> total = sum(data3) # calculate sum of data3 list elements Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: 'int' object is not callable 

Also note that sum works fine on set , there is no need to convert it to list

Answer 2

This means that somewhere else in your code there is something like:

 sum = 0 

Which hides the built-in amount (which is called) with int (which is not the case).

Answer 3

It is easy to restart it in the interpreter and fix such problems. If you do not want to restart the interpreter, there is another way to fix it:

 Python 2.6.6 (r266:84292, Dec 27 2010, 00:02:40) [GCC 4.4.5] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> l = [1,2,3] >>> sum(l) 6 >>> sum = 0 # oops! shadowed a builtin! >>> sum(l) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: 'int' object is not callable >>> import sys >>> sum = sys.modules['__builtin__'].sum # -- fixing sum >>> sum(l) 6 

This is also useful if you are assigned a value to any other built-in, such as dict or list