我们有一个很大的原始数据文件,我们想把它修剪成指定的大小。
如何在python中获取文本文件的前N行?所使用的操作系统对实现有任何影响吗?
我们有一个很大的原始数据文件,我们想把它修剪成指定的大小。
如何在python中获取文本文件的前N行?所使用的操作系统对实现有任何影响吗?
当前回答
Python 3:
with open("datafile") as myfile:
head = [next(myfile) for x in range(N)]
print(head)
Python 2:
with open("datafile") as myfile:
head = [next(myfile) for x in xrange(N)]
print head
下面是另一种方法(Python 2和3都是):
from itertools import islice
with open("datafile") as myfile:
head = list(islice(myfile, N))
print(head)
其他回答
我所做的就是用熊猫形来称呼N行。我认为性能不是最好的,但是举个例子,如果N=1000:
import pandas as pd
yourfile = pd.read_csv('path/to/your/file.csv',nrows=1000)
N = 10
with open("file.txt", "a") as file: # the a opens it in append mode
for i in range(N):
line = next(file).strip()
print(line)
这适用于Python 2和3:
from itertools import islice
with open('/tmp/filename.txt') as inf:
for line in islice(inf, N, N+M):
print(line)
Python 3:
with open("datafile") as myfile:
head = [next(myfile) for x in range(N)]
print(head)
Python 2:
with open("datafile") as myfile:
head = [next(myfile) for x in xrange(N)]
print head
下面是另一种方法(Python 2和3都是):
from itertools import islice
with open("datafile") as myfile:
head = list(islice(myfile, N))
print(head)
没有特定的方法来读取文件对象暴露的行数。
我想最简单的方法是:
lines =[]
with open(file_name) as f:
lines.extend(f.readline() for i in xrange(N))