python 每次读两行文本

  1. 方法一：enumerate()函数获得行号，用行号取余；
import time
import itertools

start1=time.perf_counter()

List1=[]
path = r"C:\Users\xx.csv"

with open(path) as f:
	for lineID, line in enumerate(f):
		if lineID % 2 == 0:
			List1.append(line)
		if lineID % 2 == 1:
			List1.append(line)

f.close()
        

print("time used= ", time.perf_counter()-start1)
  1. 方法二
  • itertools.zip_longest(*iterables, fillvalue=None)
    Make an iterator that aggregates elements from each of the iterables. If the iterables are of uneven length, missing values are filled-in with fillvalue. Iteration continues until the longest iterable is exhausted.
    聚合多个迭代对象，长度为最长的对象。
start2 = time.perf_counter()

List2 = []
with open(path) as f:
    for line1, line2 in itertools.zip_longest(*[f]*2):
    	List2.append(line1)
        List2.append(line2)
f.close()

print("time used= ",time.perf_counter() -start2)
  1. 方法三：
start3 = time.perf_counter()

List3 = []
with open(path) as f:
    while True:
        line1=f.readline()
        line2=f.readline()
        if not line2:
            break
        List3.append(line2)
f.close()

print("time used= ", time.perf_counter() - start3)

参考：

https://docs.python.org/3.8/library/itertools.html?highlight=itertools%20zip_longest#itertools.zip_longest