How to extract integers from a string separated by spaces in Python 2.7?

Question

I want to extract integers from a string in which integers are separated by blank spaces i.e ' '. How could I do that ??

Input

I='1 15 163 132'

Result:

[1,15,163,132]

So I wrote a function which goes like this

def getIt(aStr):
collect = []
i=0
while i < len(aStr):
    print('i = ' + str(i))
    if aStr[i]!=' ':
        j=0
        while aStr[i+j]!=' ' or  (i+j)<=len(aStr)-1:
            print('j = '+str(j))
            j+=1
        if i+j==len(aStr):    
            collect.append(int(aStr[i:i+j-1]))
        else:
            collect.append(int(aStr[i:i+j]))
        i+=j+1

    else:
        i+=1  
return collect

The code runs perfectly when I remove the condition

while aStr[i+j]!=' ':# or  (i+j)<=len(aStr)-1:

And place a blank space at the end of every input string. Please inform where am I going wrong?

Answer 1

Try this code:

myIntegers = [int(x) for x in I.split()]    

---

EXPLANATION:

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Where s is the string you want to split up, and a is the string you want to use as the delimeter. Then:

s.Split(a)

Splits the string s, at those points where a occurs, and returns a list of sub-strings that have been split up.

If no argument is provided, eg: s.Split() then it defaults to using whitespaces (such as spaces, tabs, newlines) as the delimeter.

Concretely, In your case:

I = '1 15 163 132'
I = I.split() 
print(I)

["1", "15", "163", "132"]

It creates a list of strings, separating at those points where there is a space in your particular example.

Here is the official python documentation on the string split() method.

---

Now we use what is known as List Comprehensions to convert every element in a list into an integer.

myNewList = [operation for x in myOtherList]

Here is a breakdown of what it is doing:

• Assuming that myOtherList is a list, with some number of elements,
• then we will temporarily store one element at a time as x
• and we will perform some operation for each element in myOtherList
• assuming that this operation we perform has some return value,
  • then the returned value will be stored as an element in a new list that we are creating
• The end result is that we will populate a new list myNewList, that is the exact same length as myOtherList

Concretely, In your case:

myIntegers = [int(x) for x in I.split()]    

Performs the following:

• We saw that I.split() returns ["1", "15", "163", "132"]
• for each of these string elements, simply convert them to an integer
• and store that integer as an element in a new list.

See the official python documentation on List Comprehensions for more information.

Hope this helps you.

Answer 2

You could simply do like this,

>>> import re
>>> I='bar 1 15 foo 163 132 foo bar'
>>> [int(i) for i in I.split() if re.match(r'^\d+$', i)]
[1, 15, 163, 132]

Without regex:

>>> I='bar 1 15 foo 163 132 foo bar'
>>> [int(i) for i in I.split() if i.isdigit()]
[1, 15, 163, 132]

i.isdigit() returns true only for the strings which contain only digits.