What substitutes xreadlines() in Python 3?

问题

In Python 2, file objects had an xreadlines() method which returned an iterator that would read the file one line at a time. In Python 3, the xreadlines() method no longer exists, and realines() still returns a list (not an iterator). Does Python 3 has something similar to xreadlines()?

I know I can do

for line in f:

instead of

for line in f.xreadlines():

But I would also like to use xreadlines() without a for loop:

print(f.xreadlines()[7]) #read lines 0 to 7 and prints line 7

回答1:

The file object itself is already an iterable.

>>> f = open('1.txt')
>>> f
<_io.TextIOWrapper name='1.txt' encoding='UTF-8'>
>>> next(f)
'1,B,-0.0522642316338,0.997268450092\n'
>>> next(f)
'2,B,-0.081127897359,2.05114559572\n'

---

Use itertools.islice to get an arbitrary element from an iterable.

>>> f.seek(0)
0
>>> next(islice(f, 7, None))
'8,A,-0.0518101108474,12.094341554\n'

回答2:

how about this (generator expression):

>>> f = open("r2h_jvs")
>>> h = (x for x in f)
>>> type(h)
<type 'generator'>`

来源：https://stackoverflow.com/questions/3541274/what-substitutes-xreadlines-in-python-3