Как найти число в строке пайтон

def get_digits(str1):
    c = ""

    for i in str1:
        if i.isdigit():
            c += i
            return c

Above is the code that I used and the problem is that it only returns only the first digit of strings. For this, I have to keep both for loop and return statement. Anyone knows how to fix?

Thanks.

it’s because your return statement is inside the for loop, so it returns after the first true if condition and stops.

  def get_digits(str1):
      c = ""
      for i in str1:
        if i.isdigit():
            c += i
      return c

answered Aug 17, 2012 at 12:15

Of course it returns only the first digit, you explicitly tell Python to return as soon as you have a digit.

Change the indentation of the return statement and it should work:

def get_digits(str1):
    c = ""

    for i in str1:
        if i.isdigit():
            c += i

    # Note the indentation here
    return c

answered Aug 17, 2012 at 12:16

there is an indentation problem which returns when it finds the first digit, as with current indentation, it is intepreted as a statement inside if statement,
it needs to be parallel to the for statement
to be considered outside for statement.

def get_digits(str1):
    c = ""

    for i in str1:
        if i.isdigit():
            c += i

    return c

digits = get_digits("abd1m4m3m22mmmbb4")
print(digits)

A curly braces equivalent of your incorrect code is :

def get_digits(str1){
    c = ""

    for i in str1 {
        if i.isdigit(){
            c += i
            return c    # Notice the error here
        }
    }
}

And when the code is corrected to move the return statement in alignment with for, the equivalent is :

def get_digits(str1){
        c = ""

        for i in str1 {
            if i.isdigit(){
                c += i               
            }
        }
        return c    # Correct as required
    }

answered Aug 17, 2012 at 12:15

Your code was almost ok, except the return statement needed to be moved to the level of your for-loop.

def get_digits(str1):
    c = ""
    for i in str1:
        if i.isdigit():
            c += i
    return c   ## <--- moved to correct level

so, now:

get_digits('this35ad77asd5')

yields:

'35775'

Explanation:

Previously, your function was returning only the first digit because when it found one the if statement was executed, as was the return (causing you to return from the function which meant you didn’t continue looking through the string).

Whitespace/indentation really matters in Python as you can see (unlike many other languages).

answered Aug 17, 2012 at 12:15