有没有更好的方法来编写这个函数？

Question

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First function returns the recursive digit sum of that number. The second function return dictionary where key is reg_dig_sum and value is count of that number occurring. when I tested it it failed giving me this

elf.assertEqual(sum_dict[0], 1) AssertionError: 0 != 1

How can I solve this?

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

def distr_of_rec_digit_sums(low=0, high=1500):
    distr = {}
    for x in range(low, high):
        if reg_dig_sum(x) not in distr:
            distr[reg_dig_sum(x)] = 0
        else:
            distr[reg_dig_sum(x)] += 1 
    return distr

Answer 1

• The problem I can think is your count for each reg_dig_sum will be one less than what it should be. That's the reason assertion condition is failing.
• You can fix this logical error by initializing distr to either 1 or by removing else condition.
• I would also suggest to use other alternatives like defaultdict to take care of initialization for you.

def distr_of_rec_digit_sums(low=0, high=1500):
    distr = {}
    for x in range(low, high):
        if reg_dig_sum(x) not in distr:
            distr[reg_dig_sum(x)] = 1 # this should be initialized to 1 for first occurance.
        else:
            distr[reg_dig_sum(x)] += 1 
    return distr

• Using defaultdict

from collections import defaultdict
def distr_of_rec_digit_sums(low=0, high=1500):
    distr = defaultdict(int)
    for x in range(low, high):
        distr[reg_dig_sum(x)] += 1 
    return distr

Answer 2

See previous comments and answers regarding changing 0 to 1

Also try to use much simpler code for reg_dig_sum with the same result:

def reg_dig_sum(n):
    return (n - 1) % 9 + 1

Answer 3

I've used a simple function to do this for a long time:

def sum_digits(num):
    if num <= 9:
        return num
    num = int(num / 10) + num - int(num / 10) * 10
    ''' takes the last digit of num off, and adds it to num. '''
    return sum_digits(num)

There are a lot of things you can find with this function. Try this on the power series, and you'll see what I mean. Really any mathematical function you could use on a number line will return interesting patterns; this function helps you see part of that.