[英]How to subtract backwards in a list in Python 3?
I am trying to subtract a list backwards in Python. 我试图在Python中向后减去列表。 This is the code:
这是代码:
list_1 = [1,2,5,7,9,85]
The subtraction should go like this: index 1 - index 0, index 2 - index 1, and so on and so forth. 减法应如下所示:索引1-索引0,索引2-索引1,依此类推。 This is the output:
这是输出:
1
3
2
2
76
How can i do something like this using Python 3? 我如何使用Python 3做类似的事情?
Using map
and operator
and itertools.islice
, this way you are avoiding intermediate lists creation or memory overhead and also avoids using python native for
loop: 使用
map
和operator
和itertools.islice
,这种方式可以避免中间列表的创建或内存开销,也可以避免使用python native for
循环:
import operator
from itertools import islice
list_1 = [1,2,5,7,9,85]
result = list(map(operator.sub, islice(list_1, 1, None),list_1))
Here you have a live example 这里有一个现场例子
使用zip
:
[i - j for i, j in zip(list_1[1:], list_1)]
You can use a good old-fashioned for loop: 您可以使用老式的for循环:
for i in range(1, len(list_1)):
print list_1[i]-list_1[i-1]
Try this: 尝试这个:
list_1 = [1,2,5,7,9,85]
for i in range(len(list_1)-1,1,-1):
list_1[i] = list_1[i]-list_1[i-1]
print(list_1)
Note: iterate backwards to get expected answer. 注意:向后迭代以获得预期的答案。
One-liner using list comprehension. 使用列表理解的一线。
Iterate from zero to the penultimate index and do the subtraction. 从零迭代到倒数第二个索引并进行减法。
[ (list_1[i+1] - list_1[i]) for i in range(len(list_1)-1)]
print [a[i+1]- a[i] for i in range(len(a)-1)]
这种单行返回一个列表,其元素是list_1中连续数字的差。
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