我的python函数不会返回值

Question

I have a user-defined function that takes table-size (m) as input. I implement an empty list (of pairs [key,count], essentially an array with two fields) of that size and use linear hashing to insert generated random numbers into the list. So say the first random number (k) is 20 and the length of the list (m) is 9, the hash function (h0 = k%m) will return 2 (as that is the remainder when 20 is divided by 9). If that cell is empty, I want to insert the key value(k) into the first field and 1 (count of probes) into the second field. If that cell is not empty, I want to increment the index using the hash function (h0 = (h0 + i)%m) until an empty cell is found and insert there. I want to return the resulting list. I have a return statement in my function and the documentation I've read says assigning a new value when I call the function and using a print statement should work. I'm using PyCharm community edition. Could my IDE be the problem? (Below is my code)

import random

def linear(m):

hTable = [[None, None] for j in range (m)]

for n in range (1100):
    k = random.randint(1,10000)

    for i in range(len(hTable)):
        for j in range(len(hTable[i])):
            h0 = k % m

            if hTable[h0] == [None,None]:
                hTable[h0][0] = k
                hTable[h0][1] = 1

            else:
                while hTable[h0] != [None, None]:
                    hTable[h0][1] += 1
                    h0 = (h0 + i)%m

                else:
                    hTable[h0][0] = k
                    hTable[h0][1] = 1

                    return hTable

                hash = linear(1223)
                print(hash)

Answer 1

>>> [None,None]*2
[None, None, None, None]

In Python, multiplying a list extends the list, it doesn't make it multidimensional. You probably wanted something like [[None, None] for i in range(m) .

(I'm also not sure what your code is doing in general, as on the first iteration everything will == [None, None] and cause your else block to be executed - which has a return in it, and thus the returned array will consist of hTable[h0] = [k, 1] and every other element [None, None] ...)

Also, h0 will have the same value through every iteration (since it's calculated from values which aren't change)... and you probably want to return hTable , not [hTable] , since it's already a list.

Answer 2

The problem was the indentation of my return statement. The following works:

import random

def linear(m):

    hTable = [[None, 0] for j in range (m)]

    nums = [random.randint(1,10001) for n in range(1100)]

    for i in range(len(nums)):
        h0 = nums[i] % m

        while hTable[h0] != [None, 0]:
            hTable[h0][1] += 1
            h0 = (h0 + 1)%m

        else:
            hTable[h0][0] = nums[i]
            hTable[h0][1] = 1

    count = sum(i[1] for i in hTable)
    print (count)

    return hTable

l = linear(1223)
print(l)