something about performence

[Terry Reedy]

On 6/20/2011 10:59 PM, king6cong at gmail.com wrote:
> Hi，
> I have two large files,each has more than 200000000 lines,and each line 
> consists of two fields,one is the id and the other a value,
> the ids are sorted.
> 
> for example:
> 
> file1
> (uin_a y)
> 1 10000245
> 2 12333
> 3 324543
> 5 3464565
> ....
> 
> 
> file2
> (uin_b gift)
> 1 34545
> 3 6436466
> 4 35345646
> 5 463626
> ....
> 
> I want to merge them and get a file,the lines of which consists of an id 
> and the sum of the two values in file1 and file2。
> the codes are as below:

One minor thing you can do is use bound methods
> 
> uin_y=open('file1')
> uin_gift=open(file2')

ynext = open('file1').next
gnext = open(file1').next

> y_line=uin_y.next()
> gift_line=uin_gift.next()

y_line = ynext()
gift_list = gnext()

and similarly for all .next appearances in what follows.

> while 1:
> try:
> uin_a,y=[int(i) for i in y_line.split()]

This creates an unnecessary second temporary  list. Unroll the loop.

pair = y_line.split
uin_a = int(pair[0])
y = int(pair[1])

> uin_b,gift=[int(i) for i in gift_line.split()]

same for this line

> if uin_a==uin_b:
> score=y+gift
> print uin_a,score
> y_line=uin_y.next()
> gift_line=uin_gift.next()
> if uin_a<uin_b:
> print uin_a,y
> y_line=uin_y.next()
> if uin_a>uin_b:
> print uin_b,gift
> gift_line=uin_gift.next()
> except StopIteration:
> break



-- 
Terry Jan Reedy