Python: convert str to integer

Question

I'm new at Python and I have an assginment which is read a file and convert it to matrix. My file is:

n 5
0 -- 3
0 -- 4
1 -- 2
1 -- 3
2 -- 4
3 -- 3

First of all,I have to make a "5X5" matrix. I read 5 like this:

f = open("graph.txt")
 mylist = f.readlines()
 a = mylist[0][2]

When say print a it prints 5. In order to make a matrix I need to convert this string to integer. However, when I used int(a) function, it remained a str. How can I change it to integer permanently?

• Tim Pietzcker: You probably also want to look into the .split() method to split strings into chunks based on whitespace. That looks like a tool you're going to need.
• AI Generated Response: What does the resultant matrix look like? Could you please post it?
• johnsyweb: Closely related: How to read numbers from file in Python?
• jdyg: When I use .split() for other lines, besides the first one, it splits last number (for example 3) with "3\n". How can I select just one item with this method? @TimPietzcker
• Tim Pietzcker: Use mylist = [line.strip().split() for line in f].

Answer 1

int creates a new value but does not change the original one. So, to actually change the value, you must do something like

list[0][2] = int(list[0][2])

Answer 2

use the int() constructor to assign to a:

a = int(list[0][2])

Note that this will raise an exception if the string cannot be converted to int.