How do i sum a list in python?

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Sum of numbers in the list is required everywhere. Python provides 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() 

Python3

numbers = [1,2,3,4,5,1,4,5]

Sum = sum(numbers)

print(Sum)

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 than numbers in the list. 

Python3

arr = ["a"]

Sum = sum(arr)

print(Sum)

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'

Python3

numbers = [1,2,3,4,5,1,4,5]

Sum = sum(numbers)

average= Sum/len(numbers)

print (average)

Output:

3

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Given a list of numbers, write a Python program to find the sum of all the elements in the list.

Example:  

Input: [12, 15, 3, 10]
Output: 40

Input: [17, 5, 3, 5]
Output: 30

Example #1: 

Python3

total = 0

list1 = [11, 5, 17, 18, 23]

for ele in range(0, len(list1)):

    total = total + list1[ele]

print("Sum of all elements in given list: ", total)

Output

Sum of all elements in given list:  74

Example #2 : Using while() loop  

Python3

total = 0

ele = 0

list1 = [11, 5, 17, 18, 23]

while(ele < len(list1)):

    total = total + list1[ele]

    ele += 1

print("Sum of all elements in given list: ", total)

Output: 
 

Sum of all elements in given list:  74

Example #3: Recursive way  

Python3

list1 = [11, 5, 17, 18, 23]

def sumOfList(list, size):

    if (size == 0):

        return 0

    else:

        return list[size - 1] + sumOfList(list, size - 1)

total = sumOfList(list1, len(list1))

print("Sum of all elements in given list: ", total)

Output

Sum of all elements in given list:  74

Example #4: Using sum() method  

Python3

list1 = [11, 5, 17, 18, 23]

total = sum(list1)

print("Sum of all elements in given list: ", total)

Output: 

Sum of all elements in given list:  74

Example 5: Using add() function of operator module

First we have to import the operator module then using the add() function of operator module adding the all values in the list. 

Python3

from operator import*

list1 = [12, 15, 3, 10]

result = 0

for i in list1:

    result = add(i, 0)+result

print(result)

Method 6: Using enumerate function

Python3

list1 = [12, 15, 3, 10];s=0

for i,a in enumerate(list1):

  s+=a

print(s)

Method 7: Using list comprehension 

Python3

list1 = [12, 15, 3, 10]

s=[i for i in list1]

print(sum(s))

Method 8: Using lambda function

Python3

list1 = [12, 15, 3, 10]

print(sum(list(filter(lambda x: (x),list1))))

Method: Using add operator 

Python3

import operator

list1 = [12, 15, 3, 10] ;s=0

for i in list1:

  s=s+operator.add(0,i)

print(s)