Python中的 sum()函数

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() 来总结列表中的数字。

句法：

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 

下面是 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

错误和异常

TypeError ：如果列表中有任何其他数字，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'

所以列表应该包含数字

实际应用：我们需要计算总和以进行进一步操作的问题，例如找出数字的平均值。

# 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