CODEWITHSUNDEEP
python
Nolan Caldwell
Nolan Caldwell

Reputation: 13

What is causing "unsupported operand type(s) for //: 'list' and 'int'"?

This is the code I have right now. I'm trying to apply a radix sort to a list of numbers read from a file and write the sorted list to a different file. 

from math import log

b = open("radix.in.txt").readlines()
a = [int(i) for i in b]

f = open("radix.out.txt", "w")
def getIndex(num, base, digit_num):
    return (num // base ** digit_num) % base  

def newLists(size):
    return [ [] for i in range(size) ]  

def order(a, base, digit_num):
    placehold = newLists(base)
    for num in a:
        placehold[getIndex(num, base, digit_num)].append(num)  
    return placehold

def radixSort(a, base):
    passes = 3
    new_list = a
    for digit_num in range(passes):
        new_list = order(new_list, base, digit_num)
    list_c = [str(i) for i in new_list]
    print list_c

radixSort(a, 10)

The input file is just a list of all the numbers to sort with one number on each line

The traceback: 

File "C:\Users\Nolan Caldwell\Desktop\HW5.py", line 23, in radixSort new_list = order(new_list, base, digit_num) 
File "C:\Users\Nolan Caldwell\Desktop\HW5.py", line 16, in order placehold[getIndex(num, base, digit_num)].append(num) 
File "C:\Users\Nolan Caldwell\Desktop\HW5.py", line 8, in getIndex return (num // base ** digit_num) % base 
TypeError: unsupported operand type(s) for //: 'list' and 'int'

Upvotes: 1

Views: 581

Answers (1)

bereal
bereal

Reputation: 34312

Your function order() expects a list of integers as a first argument a, and that's what passed in the first iteration.

However, order() returns a list of lists, and that new list is passed instead of a in the second iteration in radixSort(), that's why it fails.

Upvotes: 4

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