我有一个包含5000万行的384MB文本文件。每行包含2个空格分隔的整数:一个键和一个值。该文件按键排序。我需要一种有效的方式来查找Python中约200个键的列表的值。在Python中阅读巨大文件
我目前的做法包括在下面。它需要30秒。必须有更高效的Python foo才能将其降低到最多几秒的合理效率。
# list contains a sorted list of the keys we need to lookup
# there is a sentinel at the end of list to simplify the code
# we use pointer to iterate through the list of keys
for line in fin:
line = map(int, line.split())
while line[0] == list[pointer].key:
list[pointer].value = line[1]
pointer += 1
while line[0] > list[pointer].key:
pointer += 1
if pointer >= len(list) - 1:
break # end of list; -1 is due to sentinel
的编码二进制搜索+求解(感谢kigurai!):
entries = 24935502 # number of entries
width = 18 # fixed width of an entry in the file padded with spaces
# at the end of each line
for i, search in enumerate(list): # list contains the list of search keys
left, right = 0, entries-1
key = None
while key != search and left <= right:
mid = (left + right)/2
fin.seek(mid * width)
key, value = map(int, fin.readline().split())
if search > key:
left = mid + 1
else:
right = mid - 1
if key != search:
value = None # for when search key is not found
search.result = value # store the result of the search
我很乐意看到您的最终解决方案,因为您似乎将它放在一起,但没有提供代码的答案。 – 2009-04-13 16:47:15
在问题结束时添加 – marcog 2009-04-13 17:01:35