python - 不使用 sum() 打印整数列表的总和

Question

我在下面定义了一个函数，可以打印列表中的每个整数，并且效果很好。我想做的是创建第二个函数，该函数将调用或重新利用该int_list()函数来显示已生成列表的总和。

我不确定这是否是由代码本身固有地执行的——我对 Python 语法相当陌生。

integer_list = [5, 10, 15, 20, 25, 30, 35, 40, 45]

def int_list(self):
    for n in integer_list
        index = 0
        index += n
        print index

Answer 1

在您的代码中，您index=0在每个循环中进行设置，因此应该在for 循环之前对其进行初始化：

def int_list(grades):   #list is passed to the function
    summ = 0 
    for n in grades:
        summ += n
        print summ

输出：

int_list([5, 10, 15, 20, 25, 30, 35, 40, 45])
5
15
30
50
75
105
140
180
225

Answer 2

要获得整数列表的总和，您有几个选择。显然最简单的方法是sum，但我想你想学习如何自己做。另一种方法是在加起来时存储总和：

def sumlist(alist):
    """Get the sum of a list of numbers."""
    total = 0         # start with zero
    for val in alist: # iterate over each value in the list
                      # (ignore the indices – you don't need 'em)
        total += val  # add val to the running total
    return total      # when you've exhausted the list, return the grand total

第三个选项是reduce，它是一个函数，它本身接受一个函数并将其应用于运行总计和每个连续参数。

def add(x,y):
    """Return the sum of x and y. (Actually this does the same thing as int.__add__)"""
    print '--> %d + %d =>' % (x,y) # Illustrate what reduce is actually doing.
    return x + y

total = reduce(add, [0,2,4,6,8,10,12])
--> 0 + 2 =>
--> 2 + 4 =>
--> 6 + 6 =>
--> 12 + 8 =>
--> 20 + 10 =>
--> 30 + 12 =>

print total
42

Answer 3

integer_list = [5, 10, 15, 20, 25, 30, 35, 40, 45] #this is your list
x=0  #in python count start with 0
for y in integer_list: #use for loop to get count
    x+=y #start to count 5 to 45
print (x) #sum of the list
print ((x)/(len(integer_list))) #average

Answer 4

list = [5, 10, 15, 20, 25, 30, 35, 40, 45]

#counter 
count = 0
total = 0

for number in list:
    count += 1
    total += number
#don'n need indent
print(total)
print(count)
# average 
average = total / count
print(average)