Troubles converting from string to int python

Question

I'm working on this coding puzzle and have to covert some numbers in a string to integers to work with them. an example would be

('2 -5 7 8 10 -205')

What I tried to do was add the numbers to an empty string and convert them to an int when there was a space. Here's the code.

n is the length of the string of numbers num is the empty string I add the numbers to. Originally num=""

  while i<n:

    if temps[i]!=' ':
        num=num+temps[i]


    elif temps[i]==' ':
        print type(num)

        x=int(num)

The problem is that when it runs I get an error for the line with x=int(num) saying

ValueError: invalid literal for int() with base 10: ''

when i print num I just get numbers in a string format, so I don't understand what's wrong. Help would be really appreciated, and if you have any questions or need clarification please ask.

Thanks

karlson · Accepted Answer · 2016-01-03 20:21:19Z

6

Use str.split() to split your string at spaces, then apply int to every element:

s = '2 -5 7 8 10 -205'
nums = [int(num) for num in s.split()]

answered Jan 3, 2016 at 20:21

karlson

5,4633 gold badges33 silver badges63 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Caridorc Over a year ago

Yup, exactly what I was writing :)

TayTay · Accepted Answer · 2016-01-03 20:21:44Z

1

If your string looks like this:

s = '2 -5 7 8 10 -205'

You can create a list of ints by using a list comprehension. First you will split the string on whitespace, and parse each entry individually:

>>> [int(x) for x in s.split(' ')]
[2, -5, 7, 8, 10, -205] ## list of ints

answered Jan 3, 2016 at 20:21

TayTay

7,2385 gold badges48 silver badges69 bronze badges

Comments

David Zwicker · Accepted Answer · 2016-01-03 20:33:48Z

1

You could do this with a list comprehension:

data = ('2 -5 7 8 10 -205')
l = [int(i) for i in data.split()]
print(l)
[2, -5, 7, 8, 10, -205]

Or alternatively you could use the map function:

list(map(int, data.split()))
[2, -5, 7, 8, 10, -205]

Benchmarking:

In [725]: %timeit list(map(int, data.split()))
100000 loops, best of 3: 2.1 µs per loop

In [726]: %timeit [int(i) for i in data.split()]
100000 loops, best of 3: 2.54 µs per loop

So with map it works faster

Note: list is added to map because I'm using python 3.x. If you're using python 2.x you don't need that.

edited Jan 3, 2016 at 20:33

David Zwicker

24.4k8 gold badges68 silver badges80 bronze badges

answered Jan 3, 2016 at 20:22

Anton Protopopov

31.9k13 gold badges93 silver badges96 bronze badges

Comments

Iron Fist · Accepted Answer · 2016-01-03 20:36:26Z

1

Built-in method would do the job as well:

>>> s = '2 -5 7 8 10 -205'
>>> map(int, s.split())
[2, -5, 7, 8, 10, -205]

If Python 3+:

>>> s = '2 -5 7 8 10 -205'
>>> list(map(int, s.split()))
[2, -5, 7, 8, 10, -205]

answered Jan 3, 2016 at 20:36

Iron Fist

11k2 gold badges21 silver badges36 bronze badges

Comments

Lachezar · Accepted Answer · 2016-01-03 20:24:45Z

0

You should try to split the task into 2 subtasks:

Split the numbers in the string into list of numbers using split
Convert each of the strings in the list to a regular integer using map map

As a general advise - you should also read the documentation so that you can figure out how much of the hard work could be saved by just chaining the output of one function as an input of the next function.

answered Jan 3, 2016 at 20:24

Lachezar

6,7633 gold badges36 silver badges34 bronze badges

Collectives™ on Stack Overflow

Troubles converting from string to int python

5 Answers 5

1 Comment

Comments

Comments

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

1 Comment

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related