我尝试用python只打印文件的前5行

Question

我只想打印文件的前5行，但当行数超过5行时，它会多次打印这些行。下面是我的代码：

numLines = 0
with open("points_sorted", "r") as f:
  for line in f:
    pointsList = line.split()
    numLines += 1
    if numLines >= 5:
      from itertools import islice
      with open("points_sorted") as myfile:
        head = list(islice(myfile, 5))
        print(head)

这是我的档案：

101 
87 M
71 Ko
55 Ko
15 Ko
15 M
0 M Ko

有人能帮我完成我的程序吗？

Answer 1

在满足条件后，可以使用break语句退出循环：

numLines = 0
with open("points_sorted", "r") as f:
  for line in f:
    pointsList = line.split()
    numLines += 1
    if numLines >= 5:
      break

您还可以使用enumerate()，这样就不必手动计算行数：

with open("points_sorted", "r") as f:
  for numLines, line in enumerate(f):
    pointsList = line.split()
    if numLines >= 4: # counting now starts at 0 instead of 1
      break

Answer 2

你可以这样试一试

f.readline()允许两个人逐行读取文件

with open("points_sorted", "r") as f:
 cnt = 5
 while(cnt > 0):
   pointsList = f.readline().split()
   cnt = cnt -1

您可以在while循环之间进行任何操作，并根据需要修改计数