更快地将所有项目添加到数组然后将数组写入文件，还是更快地将项目写入文件然后一次添加到数组？答案

【问题标题】：Faster to add all items to an array then write the array to file, or faster to write the item to a file and then add to array one at a time?更快地将所有项目添加到数组然后将数组写入文件，还是更快地将项目写入文件然后一次添加到数组？
【发布时间】：2014-01-31 17:53:37
【问题描述】：

所以现在我有这个（在 Python 2.7 中）：

if y == ports[0]:
   Array1.append(x)
 elif y == ports[1]:
   Array2.append(x)
 elif y == ports[2]:
   Array3.append(x)
 elif y == ports[3]:
   Array4.append(x)
 else:
   Array5.append(x)

for x in Array1:
    target=open('Array1.csv', 'a')
    target.write(x + ",\n")
    target.close()
    print "Added IP address " + x + " to Array1.csv\n"

for x in Array2:
 target=open('Array2.csv', 'a')
 target.write(x + ",\n")
 target.close()
 print "Added IP address " + x + " to Array2.csv\n"

for x in Array3:
 target=open('Array3.csv', 'a')
 target.write(x + ",\n")
 target.close()
 print "Added IP address " + x + " to Array3.csv\n"

for x in Array4:
  target=open('Array4.csv', 'a')
  target.write(x + ",\n")
  target.close()
  print "Added IP address " + x + " to Array4.csv\n"

for x in Array5:
  target=open('Array5.csv', 'a')
  target.write(x + ",\n")
  target.close()
  print "Added IP address " + x + " to Array5.csv\n"

如果我这样做，程序会更快完成吗：

if y == ports[0]:
    Array1.append(x)
    target=open('Array1.csv', 'a')
    target.write(x + ",\n")
    target.close()
    print "Added IP address " + x + " to Array1.csv\n"
elif y == ports[1]:
    Array2.append(x)
    target=open('Array2.csv', 'a')
    target.write(x + ",\n")
    target.close()
    print "Added IP address " + x + " to Array2.csv\n"
elif y == ports[2]:
    Array3.append(x)
    target=open('Array3.csv', 'a')
    target.write(x + ",\n")
    target.close()
    print "Added IP address " + x + " to Array3.csv\n"
elif y == ports[3]:
    Array4.append(x)
    target=open('Array4.csv', 'a')
    target.write(x + ",\n")
    target.close()
    print "Added IP address " + x + " to Array4.csv\n"
else:
    Array5.append(x)
    target=open('Array5.csv', 'a')
    target.write(x + ",\n")
    target.close()
    print "Added IP address " + x + " to Array5.csv\n"

或者我会发现有什么不同吗？或者也许有第三种更快的方法？将项目写入列表时是否重要？

【问题讨论】：

你为什么不直接测量一下？
无论哪种情况，我都有一个建议。不是有五个变量Array1 到Array5，而是有一个列表Arrays，其中包含五个数组。那么您的第一个代码可能是for i in range(5): for x in Array[i]:，而不是连续五个循环。

标签： python arrays file

【解决方案1】：

这可能无关紧要。更重要的是不要不断地重新打开文件：

with open('Array1.csv', 'a') as target:
    for x in Array1:
        target.write(x + ",\n")
        print "Added IP address " + x + " to Array1.csv\n"

另外，我不知道它是否适用于此，但the csv module 确实存在。

【讨论】：