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)

如果你想快速读取第一行并且不关心性能，你可以使用.readlines()返回列表对象，然后对列表进行切片。

例如，前5行:

with open("pathofmyfileandfileandname") as myfile:
    firstNlines=myfile.readlines()[0:5] #put here the interval you want

注意:整个文件是读取的，所以不是最好的从性能的角度来看，但它 是易于使用，快速编写和易于记忆，所以如果你只是想执行 一些一次性计算非常方便

print firstNlines

与其他答案相比，一个优点是可以轻松地选择行范围，例如跳过前10行[10:30]或最后10行[:-10]或只选择偶数行[::2]。

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))

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)

对于前5行，简单地做:

N=5
with open("data_file", "r") as file:
    for i in range(N):
       print file.next()