adding numbers in a string and multiplying by 2 in python

Question

I am trying to add the digits from a string and multiply it by 2.

ex) "123" would be (1+2+3)*2

I have tried this but I can't seem to get it working.

def add_digits_in_string(dig):
    initial = 0
    strinitial = str(initial)
    for i in dig:
        t = str(i)
        if t.isdigit():
            strinitial += int(t)
            strinitial*2
    return strinitial

Answer 1

your code

def adddigitsinstring(dig): # dig is string "123"

    initial = 0 # initial is of type int
    strinitial = str(initial) # converting initial to string type into new varibale strinitial
    for i in dig: # looping through each digit in the dig
        t = str(i) # converting existing string to string , not required
        if t.isdigit(): # check if digit char is digit 

            strinitial += int(t) # adding the int type with the str type wrong "2 +"2" == error 
            strinitial*2 # multiple value with the 2, so in every loop it got multiple each time , not required


    return strinitial # return int value as str type ie "123"

this is what you should do, you need to keep checking the if each character in the input is a digit or not. if it is a digit then you need to keep adding the digits to a intial value of type int beacuse 1+1=2 and '1'+'1' ='11', once you add all the digits then multiply them by 2 and return the result in str format

def adddigitsinstring(dig:str):
    intial  = 0
    for digit in dig:
        if digit.isdigit():
            intial += int(digit)
    final_result = intial * 2
    return str(final_result)

def add_digits_in_string(dig:str):
    digit = [int(digi) for digi in list(dig) if digi.isdigit()]
    return str(sum(digit) * 2)


print(adddigitsinstring("12345"))

print(add_digits_in_string("12345"))

output

30
30

Answer 2

You can use built-in function sum , list expansion and int to convert a digit to a string. You can iterate over consecutive characters easily.

In [8]: s = "123"

In [9]: 2*sum([int(ss) for ss in s])
Out[9]: 12

Answer 3

You don't need that strinitial variable, only an int where to store the partial sum:

def adddigitsinstring(dig):
    sum=0
    for i in dig:
        if i.isdigit():
             sum=sum + int(i)
    return sum * 2

Answer 4

Try this using list comprehension :

num = '123'
print(sum(int(x) for x in num)*2)

and here you are if you really need that in a function:

def adddigitsinstring(dig):
    return sum(int(x) for x in dig)*2

num = '123'
print(adddigitsinstring(num))

Answer 5

You can sum a list comprehension the return the result multiplied by 2

def adddigitsinstring(dig):
    return sum([int(i) for i in dig if i.isdigit()]) * 2

print(adddigitsinstring("123"))

Answer 6

The most simple I could come up with:

def adddigitsinstring(dig):
  return 2*sum(map(lambda x:int(x), dig))

Sample tests:

>>> adddigitsinstring("1234")
20
>>> adddigitsinstring("9")
18