有没有更好的方法来解析python文件？

Question

I am looking for some better way to parse a huge file. Following is the example of the file.

sample.txt

'abcdefghi'
'xyzwfg'
'lmnop'

Out of which I am looking for 'abc' and 'xyz' in the file at least once

I was able to find them but I am looking for some better way. Following is my code

datafile = file('sample.txt')
abc = 0
xyz = 0
found - True

for line in datafile:
        if 'abc' in line:
            abc += 1
            break    
for line in datafile:
        if 'xyz' in line:
            xyz += 1
            break

if (abc + xyz) >= 2:
    print 'found'
else:
    print 'fail'

I am running a loop twice. So is there a better way to parse the file?

Answer 1

Your current code will produce incorrect results if you 'xyz' occurs before 'abc' . To fix this test for both in the same loop.

with open('sample.txt') as datafile:
    abc_found = False
    xyz_found = False

    for line in datafile:
        if 'abc' in line:
            abc_found = True
        if 'xyz' in line:
            xyz_found = True
        if abc_found and xyz_found: 
            break # stop looking if both found

Answer 2

"Better" is subjective and there are no metrics provided to define it. However, a simple optimization is the following:

for line in datafile:
    if 'abc' in line:
        abc += 1
    if 'xyz' in line:
        xyz += 1

If the actual problem is that the file is indeed very large, you want to only read one line at a time:

f = open('myTextFile.txt', "r")
line = f.readline()
while line:
    if 'abc' in line:
        abc += 1
    if 'xyz' in line:
        xyz += 1
    line = f.readline()

The result of this would be to get the number of lines in which abc and xyz occurred, respectively. If the idea is to quit as soon as you find a single matching line, then including the break is appropriate.