产生文本文件交替行的 Pythonic 方法

Question

我有一个文本文件如下，我想生成奇数/偶数行:

this is a blah 
 I don't care,
whatever foo bar
ahaha

我已经尝试检查枚举索引的奇数/偶数，但是在文本文件中生成交替行的 pythonic 方法是什么？我试过:

text = "this is a blah \n I don't care,\nwhatever foo bar\nahaha"
with open('test.txt', 'w') as fout:
    for i in text.split('\n'):
        print>>fout, i

def yield_alt(infile, option='odd'):
    with open(infile,'r') as fin:
        for i,j in enumerate(fin):
            if option=='odd':
                if i+1 & 0x1:
                    yield j
            elif option=='even':
                if i & 0x1:
                    yield j

for i in yield_alt('test.txt'):
    print i

[输出]:

this is a blah 

whatever foo bar

最后，i & 0x1 是什么意思？我知道它会检查偶数，还有其他检查偶数的方法吗？

Answer 1

另一种方法是使用 iterools.islice 对文件对象进行切片:

>>> from itertools import islice
>>> def yield_alt(f, option='odd'):
        if option == 'odd':
            return islice(f, 0, None, 2)
        return islice(f, 1, None, 2)
... 
>>> with open('abc1') as f:
    for line in yield_alt(f):      
        print line,
...         
this is a blah 
whatever foo bar

>>> with open('abc1') as f:
    for line in yield_alt(f, 'even'):
        print line,
...         
 I don't care,
ahaha