匯總列表中的值（python）

Question

大家好，我在嘗試對列表中的所有值求和時遇到麻煩。 我不確定這是否首先可能。

dL= list(csv.reader(input))
sL = dL [14247:14611]
a = [row[5] for row in sL[1:]] 
print a

這段代碼是我到目前為止所擁有的，並產生結果

['5.0', '0.0', '0.0', '0.0', '0.0', '1.6', '4.4', '14.0', '0.0', '0.0', '0.8', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.2', '0.0', '0.0', '0.0', '0.0', '95.6', '63.6', '0.0', '0.0', '0.0', '9.0', '0.0', '0.0', '0.0', '0.0', '20.2', '14.4', '1.6', '0.0', '7.6', '2.4', '0.0', '11.4', '0.0', '79.4', '60.4', '27.2', '', '1.8', '0.0', '0.0', '29.6', '67.6', '2.2', '0.0', '0.0', '0.0', '14.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '', '3.2', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '6.2', '0.0', '0.0', '0.0', '0.8', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.2', '11.8', '2.4', '0.0', '0.0', '0.0', '0.4', '16.8', '8.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '2.6', '27.2', '77.0', '0.2', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.2', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '9.2', '2.6', '0.0', '0.2', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.2', '0.0', '0.0', '0.0', '0.0', '0.2', '0.0', '0.0', '0.0', '0.0', '1.6', '0.0', '0.0', '0.0', '0.0', '0.0', '6.8', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '', '', '', '', '', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '37.8', '0.2', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0']

上面的列表沒有鍵入，而是由功能代碼生成的。 這會影響結果嗎？

任何人都可以幫助我向我展示如何解決此問題，並將所有這些值加到此列表中的代碼中。 我相信我必須加入字符串，但是不確定。 您能否告訴我是否可以對列表的所有這些值求和，如果可以，我該怎么做？

編輯：

THANKS FOR ALL THE HELP GUYS 

Answer 1

我會使用math.fsum來獲得更准確的總和：

>>> nums = ['5.0', '0.0', '0.0', '0.0', '0.0', '1.6', '4.4', '14.0', '0.0', '0.0', '0.8', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.2', '0.0', '0.0', '0.0', '0.0', '95.6', '63.6', '0.0', '0.0', '0.0', '9.0', '0.0', '0.0', '0.0', '0.0', '20.2', '14.4', '1.6', '0.0', '7.6', '2.4', '0.0', '11.4', '0.0', '79.4', '60.4', '27.2', '', '1.8', '0.0', '0.0', '29.6', '67.6', '2.2', '0.0', '0.0', '0.0', '14.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '', '3.2', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '6.2', '0.0', '0.0', '0.0', '0.8', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.2', '11.8', '2.4', '0.0', '0.0', '0.0', '0.4', '16.8', '8.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '2.6', '27.2', '77.0', '0.2', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.2', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '9.2', '2.6', '0.0', '0.2', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.2', '0.0', '0.0', '0.0', '0.0', '0.2', '0.0', '0.0', '0.0', '0.0', '1.6', '0.0', '0.0', '0.0', '0.0', '0.0', '6.8', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '', '', '', '', '', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '37.8', '0.2', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0', '0.0']
>>> from math import fsum
>>> fsum(float(n or 0.0) for n in nums)
749.8

相對於

>>> sum(float(n or 0.0) for n in nums)
749.8000000000003

使用您的代碼，無需立即將整個文件保存到內存中的更有效方式：

from itertools import islice
dL= csv.reader(input)
sL = islice(dL, 14247+1, 14611)    
a = [row[5] for row in sL] 
print fsum(float(n or 0.0) for n in a)

Answer 2

您可以將所有數字與sum但需要先將字符串轉換為浮點數，然后檢查空字符串：

sum(float(x) for x in a if x)

Answer 3

這也適用：

reduce(lambda x,y:x+y, map(float, filter(lambda x:x!='', a)))