Python计算大文件行数方法及性能比较

如何使用Python快速高效地统计出大文件的总行数, 下面是一些实现方法和性能的比较。

1.readline读所有行使用readlines方法读取所有行:

def readline_count(file_name): return len(open(file_name).readlines())
2.依次读取每行依次读取文件每行内容进行计数:

def simple_count(file_name): lines = 0 for _ in open(file_name): lines += 1 return lines
3.sum计数使用sum函数计数:

def sum_count(file_name): return sum(1 for _ in open(file_name))
4.enumerate枚举计数:

def enumerate_count(file_name): with open(file_name) as f: for count, _ in enumerate(f, 1): pass return count
5.buff count 每次读取固定大小,然后统计行数:

def buff_count(file_name): with open(file_name, 'rb') as f: count = 0 buf_size = 1024 * 1024 buf = f.read(buf_size) while buf: count += buf.count(b'\n') buf = f.read(buf_size) return count
6.wc count 调用使用wc命令计算行:

def wc_count(file_name): import subprocess out = subprocess.getoutput("wc -l %s" % file_name) return int(out.split()[0])
7.partial count 在buff_count基础上引入partial:

def partial_count(file_name): from functools import partial buffer = 1024 * 1024 with open(file_name) as f: return sum(x.count('\n') for x in iter(partial(f.read, buffer), ''))
8.iter count 在buff_count基础上引入itertools模块 :

def iter_count(file_name): from itertools import (takewhile, repeat) buffer = 1024 * 1024 with open(file_name) as f: buf_gen = takewhile(lambda x: x, (f.read(buffer) for _ in repeat(None))) return sum(buf.count('\n') for buf in buf_gen)