How do you sum parts of a list in python?

Question

weekly = [ sum(visitors[x:x+7]) for x in range(0, len(daily), 7)]

Or slightly less densely:

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How do you sum the components of a list in Python?
How do you find the sum of a list of elements?
How do I get part of a list in Python?

weekly = []
for x in range(0, len(daily), 7):
     weekly.append( sum(visitors[x:x+7]) )

Alternatively, using the numpy module.

by_week = numpy.reshape(visitors, (7, -1))
weekly = numpy.sum( by_week, axis = 1)

Note that this requires the number of elements in visitor be a multiple of 7. It also requires that you install numpy. However, its probably also more efficient then the other approaches.

Or for itertools code bonus:

def grouper(n, iterable, fillvalue=None):
    "grouper(3, 'ABCDEFG', 'x') --> ABC DEF Gxx"
    args = [iter(iterable)] * n
    return itertools.izip_longest(fillvalue=fillvalue, *args)

weekly = map(sum, grouper(7, visitors, 0))

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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'

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.

Python3

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

Sum = sum(numbers)

average= Sum/len(numbers)

print (average)

Output:

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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)

How do you sum the components of a list in Python?

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.

How do you find the sum of a list of elements?

Algorithms.

def sum_of_list(l): total = 0. for val in l: total = total + val. return total. my_list = [1,3,5,2,4] ... .

def sum_of_list(l,n): if n == 0: return l[n]; return l[n] + sum_of_list(l,n-1) my_list = [1,3,5,2,4] ... .

my_list = [1,3,5,2,4] print "The sum of my_list is", sum(my_list) Run..

How do I get part of a list in Python?

How to Get Specific Elements From a List?.

Get elements by index. use the operator [] with the element's index. use the list's method pop(index) use slicing lst[start:stop:step] to get several elements at once. ... .

Get elements by condition. use the filter() function. use a list comprehension statement..

programming python Sum list Python