列表中的数字总和在任何地方都是必需的。 Python提供了一个内置函数sum()，用于对列表中的数字求和。

用法:

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.

可能的两种语法：

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

以下是sum()的Python实现

# 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)

输出：

25
35
Error and Exceptions

TypeError：如果列表中没有数字，则会引发此错误。

# 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)

运行时错误：

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

因此列表应包含数字

实际应用：需要计算总和以进行进一步运算(例如找出数字的平均值)的问题。

# 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

输出：

3