CODEWITHSUNDEEP
pythonstringinttype-conversion
Arete
Arete

Reputation: 13

Troubles converting from string to int python

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

Upvotes: 1

Views: 182

Answers (5)

Iron Fist
Iron Fist

Reputation: 10951

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]

Upvotes: 1

Anton Protopopov
Anton Protopopov

Reputation: 31662

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.

Upvotes: 1

Lachezar
Lachezar

Reputation: 6703

You should try to split the task into 2 subtasks:

  1. Split the numbers in the string into list of numbers using split
  2. 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.

Upvotes: 0

TayTay
TayTay

Reputation: 7160

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

Upvotes: 1

karlson
karlson

Reputation: 5433

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()]

Upvotes: 6

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