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sum() function in Python
• Difficulty Level : Easy
• Last Updated : 23 Nov, 2020

Sum of numbers in the list is required everywhere. Python provide an inbuilt function sum() which sums up the numbers in the list.

Syntax:

```sum(iterable, start)
iterable : iterable can be anything list , tuples or dictionaries ,
but most importantly it should be numbers.
start : this start is added to the sum of
numbers in the iterable.
If start is not given in the syntax , it is assumed to be 0.```

Possible two syntaxes:

```sum(a)
a is the list , it adds up all the numbers in the
list a and takes start to be 0, so returning
only the sum of the numbers in the list.
sum(a, start)
this returns the sum of the list + start
```

Below is the Python implementation of the sum()

 `# Python code to demonstrate the working of ``# sum()``  ` `numbers ``=` `[``1``,``2``,``3``,``4``,``5``,``1``,``4``,``5``]`` ` `# start parameter is not provided``Sum` `=` `sum``(numbers)``print``(``Sum``)`` ` `# start = 10``Sum` `=` `sum``(numbers, ``10``)``print``(``Sum``)`

Output:

```25
35
```

Error and Exceptions

TypeError : This error is raised in the case when there is anything other then numbers in the list.

 `# Python code to demonstrate the exception of ``# sum()``arr ``=` `[``"a"``]`` ` `# start parameter is not provided``Sum` `=` `sum``(arr)``print``(``Sum``)`` ` `# start = 10``Sum` `=` `sum``(arr, ``10``)``print``(``Sum``)`

Runtime Error :

```Traceback (most recent call last):
File "/home/23f0f6c9e022aa96d6c560a7eb4cf387.py", line 6, in
Sum = sum(arr)
TypeError: unsupported operand type(s) for +: 'int' and 'str'
```

So the list should contain numbers

Practical Application: Problems where we require sum to be calculated to do further operations such as finding out the average of numbers.

 `# Python code to demonstrate the practical application``# of sum()`` ` `numbers ``=` `[``1``,``2``,``3``,``4``,``5``,``1``,``4``,``5``]`` ` `# start = 10``Sum` `=` `sum``(numbers)``average``=` `Sum``/``len``(numbers) ``print` `(average)`

Output:

```3
```

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