从Python中的文件中读取包含整数的行？ [英] Read lines containing integers from a file in Python?

问题描述

我有这样的文件格式：

  9 8 1 
 3 4 1 
。 .. 
 ... 
  

现在我想把每一行看作三个整数。

当我在f.readlines（）中使用

  ：
 print line.split（）
  

脚本输出：

  ['9'，'8'，'1 \r\\\
'] 
 ['3'，' 4'，'1 \r\\\
'] 
 ... 
 ... 
  

如何将每一行作为三个整数？

如何将列表转换为整数：

你可以遍历每一行并将字符串转换为 int 以下示例使用列表理解：

Gi ven：

  line = ['3'，'4'，'1 \r\\\
'] 
  

然后：

  int_list = [int（i）for i in line] 
  

将产生一个整数列表

  [3,4,1] 
  

，然后您可以通过下标（0到2）进行访问。例如
$ b

int_list [0] 包含 3 ， p>

int_list [1] 包含 4 ，

etc。

---

一个更简化的版本供您考虑：

  with open（'data.txt'）as f：
 for line in f：
 int_list = [int （i）for line in line.split（）] 
 print int_list 
  

使用和是因为它会在你完成后自动关闭你的文件，或者遇到异常。

<根据你的意见，如果你想在3个不同的变量，例如一个数字 ， b 和 c ，您可以执行以下操作：

  for line in f：
a，b，c = [int（i）for line in line.split（）] 
打印'a =％d，b =％d，c =％d\\\
'％（a，b，c）
  

得到这个：

$ $ $ $ $ $ c $ a = 9，b = 8，c = 1


这个数字在每行有3个数字。

注意，代替list comprehension（LC），您也可以使用生成器表达式 （GE）：

  a，b，c =（int（i）for i in line.split（） ）
  

对于3个整数的特定问题，这并没有太大的区别，但是我展示了它完整性。对于较大的问题，LC需要更多的内存，因为它一次生成一个完整的内存列表，而GE根据需要逐个生成一个值。这个问题生成器表达式与列表理解将给你更多的信息，如果你很好奇。

I have a file format like this:

9 8 1
3 4 1
...
...

Now, I want to get each line as three integers.

When I used

for line in f.readlines():
    print line.split(" ")

The script printed this:

['9', '8', '1\r\n']
['3', '4', '1\r\n']
...
...

How can I get each line as three integers?

解决方案

Using the code you have and addressing your specific question of how to convert your list to integers:

You can iterate through each line and convert the strings to int with the following example using list comprehension:

Given:

line =['3', '4', '1\r\n']

then:

int_list = [int(i) for i in line]

will yield a list of integers

[3, 4, 1]

that you can then access via subscripts (0 to 2). e.g.

int_list[0] contains 3,

int_list[1] contains 4,

etc.

---

A more streamlined version for your consideration:

with open('data.txt') as f:
    for line in f:
        int_list = [int(i) for i in line.split()]
        print int_list

The advantage of using with is that it will automatically close your file for you when you are done, or if you encounter an exception.

UPDATE:

Based on your comments below, if you want the numbers in 3 different variables, say a, b and c, you can do the following:

   for line in f:
       a, b, c = [int(i) for i in line.split()]
       print 'a = %d, b = %d, c = %d\n' %(a, b, c)

and get this:

    a = 9, b = 8, c = 1

This counts on there being 3 numbers on each line.

Aside:

Note that in place of "list comprehension" (LC) you can also use a "generator expression" (GE) of this form:

    a, b, c = (int(i) for i in line.split())

for your particular problem with 3 integers this doesn't make much difference, but I show it for completeness. For larger problems, LC requires more memory as it generates a complete list in memory at once, while GE generate a value one by one as needed. This SO question Generator Expressions vs. List Comprehension will give you more information if you are curious.

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