sezina - 9 months ago 26

Python Question

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?

Answer

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.