你如何在python中添加一系列数字
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How do you add a range of numbers in python
提问by user2803555
I have a list of odd numbers but I still need to add them:
我有一个奇数列表，但我仍然需要添加它们：
for n in range(100, 200):
if n % 2 == 1:
print sum([n])
采纳答案by sberry
If you are looking to sum the odd numbers in the range of 100 to 200, then the most straight forward way would be:
如果您想对 100 到 200 范围内的奇数求和，那么最直接的方法是：
sum(range(101, 200, 2))
Start at 101 (odd), go till 199 (odd) and increment by 2 so that each number is odd. For instance,
从 101（奇数）开始，一直到 199（奇数）并加 2，使每个数字都是奇数。例如，
>>> range(101, 110)
[101, 102, 103, 104, 105, 106, 107, 108, 109]
Then you can just sum them.
然后你可以把它们相加。
If you have a preexisting list of numbers then either of the two following methods should fit your need:
如果您有一个预先存在的数字列表，那么以下两种方法中的任何一种都应该适合您的需要：
>>> nums = [1, 2, 4, 5, 6, 9, 11, 15, 20, 21]
>>> sum(filter(lambda x: x % 2, nums))
62
>>> sum(num for num in nums if num % 2)
62
And this is probably what you were trying to do:
这可能就是你想要做的：
>>> total = 0
>>> for num in nums:
... if num % 2:
... total += num
...
>>> total
62
回答by Paul Hankin
The sum of all numbers from 1 to N (inclusive)is N * (N + 1) / 2.
从 1 到 N（含）的所有数字之和为 N * (N + 1) / 2。
def sum_all(N):
return N * (N + 1) // 2
The sum of all even numbers from 1 to N (inclusive) is double the sum of all numbers from 1 to N//2.
从 1 到 N（含）的所有偶数之和是从 1 到 N//2 的所有数字之和的两倍。
def sum_even(N):
return sum_all(N // 2) * 2
The sum of all odd numbers from 1 to N (inclusive) is the difference of these.
从1到N（含）的所有奇数之和就是这些的差。
def sum_odd(N):
return sum_all(N) - sum_even(N)
Finally, the sum of all odd numbers between a and b is the sum of all odd numbers from 1 to b minus the sum of all odd numbers from 1 to a - 1.
最后，a 和 b 之间所有奇数的总和是从 1 到 b 的所有奇数之和减去从 1 到 a - 1 的所有奇数之和。
def sum_odd_range(a, b):
return sum_odd(b) - sum_odd(a - 1)
To answer the original question:
要回答原始问题：
print sum_odd_range(100, 199)
Note that unlike solutions using sum(), these are O(1) and will be arbitrarily faster for larger inputs.
请注意，与使用 sum() 的解决方案不同，这些是 O(1) 并且对于更大的输入将任意快。
