Sum the digits of a number - python

问题

If I want to find the sum of the digits of a number, i.e. :

Input: 932
Output: 14, which is (9 + 3 + 2)

What is the fastest way of doing this?

I instinctively did:

sum(int(digit) for digit in str(number))

and I found this online:

sum(map(int, str(number)))

Which is best to use for speed, and are there any other methods which are even faster?

回答1:

You can do it purely in integers, and it will be the most efficient:

def sum_digits(n):
    s = 0
    while n:
        s += n % 10
        n //= 10
    return s

or with divmod:

def sum_digits2(n):
    s = 0
    while n:
        n, remainder = divmod(n, 10)
        s += remainder
    return s

But both lines you posted are fine.

Even faster is the version without augmented assignments:

def sum_digits3(n):
   r = 0
   while n:
       r, n = r + n % 10, n // 10
   return r

> %timeit sum_digits(n)
1000000 loops, best of 3: 574 ns per loop

> %timeit sum_digits2(n)
1000000 loops, best of 3: 716 ns per loop

> %timeit sum_digits3(n)
1000000 loops, best of 3: 479 ns per loop

> %timeit sum(map(int, str(n)))
1000000 loops, best of 3: 1.42 us per loop

> %timeit sum([int(digit) for digit in str(n)])
100000 loops, best of 3: 1.52 us per loop

> %timeit sum(int(digit) for digit in str(n))
100000 loops, best of 3: 2.04 us per loop

回答2:

If you want to keep summing the digits until you get a single-digit number (one of my favorite characteristics of numbers divisible by 9) you can do:

def digital_root(n):
    x = sum(int(digit) for digit in str(n))
    if x < 10:
        return x
    else:
        return digital_root(x)

Which actually turns out to be pretty fast itself...

%timeit digital_root(12312658419614961365)

10000 loops, best of 3: 22.6 µs per loop

回答3:

This might help

def digit_sum(n):
    num_str = str(n)
    sum = 0
    for i in range(0, len(num_str)):
        sum += int(num_str[i])
    return sum

回答4:

Doing some Codecademy challenges I resolved this like:

def digit_sum(n):
arr = []
nstr = str(n)
for x in nstr:
    arr.append(int(x))
return sum(arr)

回答5:

You can also use this:

def sum_digits(num):
    num = str(num)
    digitSum = 0
    for i in num:
        digitSum += int(i)
    return digitSum
print sum_digits(875)

回答6:

def digitsum(n):
    result = 0
    for i in range(len(str(n))):
        result = result + int(str(n)[i:i+1])
    return(result)

"result" is initialized with 0.

Inside the for loop, the number(n) is converted into a string to be split with loop index(i) and get each digit. ---> str(n)[i:i+1]

This sliced digit is converted back to an integer ----> int(str(n)[i:i+1])

And hence added to result.

回答7:

def sumOfDigits():

    n=int(input("enter digit:")) 
    sum=0
    while n!=0 :

        m=n%10
        n=n/10
        sum=int(sum+m)

    print(sum)

sumOfDigits()

回答8:

you can also try this with built_in_function called divmod() ;

number = int(input('enter any integer: = '))
sum = 0
while number!=0: 
    take = divmod(number, 10) 
    dig = take[1] 
    sum += dig 
    number = take[0] 
print(sum)

you can take any number of digit

回答9:

Found this on one of the problem solving challenge websites. Not mine, but it works.

num = 0 #replace 0 with whatever number you want to sum up print(sum([int(k) for k in str(num)]))

回答10:

reduce(op.add,map(int,list(str(number))))

Test:

from datetime import datetime
number=49263985629356279356927356923569976549123548126856926293658923658923658923658972365297865987236523786598236592386592386589236592365293865923876592385623987659238756239875692387659238756239875692856239856238563286598237592875498259826592356923659283756982375692835692385653418923564912354687123548712354827354827354823548723548235482735482354827354823548235482354823548235482735482735482735482354823548235489235648293548235492185348235481235482354823548235482354823548235482354823548234



startTime = datetime.now()

for _ in  range(0,100000) :
    out=reduce(op.add,map(int,list(str(number))))

now=datetime.now()
runningTime=(now - startTime)

print ("Running time:%s" % runningTime)
print(out)

Running time:0:00:13.122560 2462

回答11:

Try this

    print(sum(list(map(int,input("Enter your number ")))))

回答12:

num = 123
dig = 0
sum = 0
while(num > 0):
  dig = int(num%10)
  sum = sum+dig
  num = num/10

print(sum) // make sure to add space above this line

回答13:

You can try this

def sumDigits(number):
    sum = 0
    while(number>0):
        lastdigit = number%10
        sum += lastdigit
        number = number//10

    return sum

回答14:

n = str(input("Enter the number\n"))

list1 = []

for each_number in n:

        list1.append(int(each_number))

print(sum(list1))

来源：https://stackoverflow.com/questions/14939953/sum-the-digits-of-a-number-python

标签

python

sum

digits