python - Is there a faster pythonic method to read first few lines of file than fid.readline()? -


i have open several thousand files, read first 3 lines.

currently, doing this:

def test_readline(filename):     fid = open(filename, 'rb')     lines = [fid.readline() in range(3)]

which yields result:

the slowest run took 10.20 times longer fastest. mean intermediate result being cached. 10000 loops, best of 3: 59.2 µs per loop

an alternate solution convert fid list:

def test_list(filename):     fid = open(filename, 'rb')     lines = list(fid)   %timeit test_list(myfile)

the slowest run took 4.92 times longer fastest. mean intermediate result being cached. 10000 loops, best of 3: 374 µs per loop

yikes!! there faster way read first 3 lines of these files, or readline() best? can respond alternatives , timings please?

but @ end-of-the-day have open thousands of individual files , not cached. thus, matter (looks does)?

(603µs uncached method readline vs. 1840µs list method)

additionally, here readlines() method:

def test_readlines(filename):     fid = open(filename, 'rb')     lines = fid.readlines()      return lines

the slowest run took 7.17 times longer fastest. mean intermediate result being cached. 10000 loops, best of 3: 334 µs per loop

you can slice iterable itertools.islice:

import itertools   def test_list(filename):     open(filename, 'r', encoding='utf-8') f:         return list(itertools.islice(f, 3))

(i changed open bit because it’s unusual read files in binary mode line, can revert that.)


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