Python QuicKSort代码错误

Question

this is quick sort code i found on http://interactivepython.org/runestone/static/pythonds/SortSearch/TheQuickSort.html

its giving error on line 5 ? whats wrong ? please help/.

def quickSort(alist):
   quickSortHelper(alist,0,len(alist)-1)

def quickSortHelper(alist,first,last):
   if first= pivotvalue and \
               rightmark >= leftmark:
           rightmark = rightmark -1

       if rightmark < leftmark:
           done = True
       else:
           temp = alist[leftmark]
           alist[leftmark] = alist[rightmark]
           alist[rightmark] = temp

   temp = alist[first]
   alist[first] = alist[rightmark]
   alist[rightmark] = temp


   return rightmark

alist = [54,26,93,17,77,31,44,55,20]
quickSort(alist)
print(alist)

Answer 1

Use == to test for equality. = is for variable assignment

Answer 2

The code on that website is broken. You cannot even run it on the site itself. Here is the correct code . I ran it without errors.

def quickSort(alist):
    quickSortHelper(alist,0,len(alist)-1)
def quickSortHelper(alist,first,last):
    if first<last:
        splitpoint = partition(alist,first,last)
        quickSortHelper(alist,first,splitpoint-1)
        quickSortHelper(alist,splitpoint+1,last)

def partition(alist,first,last):
    pivotvalue = alist[first]
    leftmark = first+1
    rightmark = last
    done = False
    while not done:
        while leftmark <= rightmark and alist[leftmark] < pivotvalue:
            leftmark = leftmark + 1
        while alist[rightmark] > pivotvalue and rightmark >= leftmark:
            rightmark = rightmark -1
        if rightmark < leftmark:
            done = True
        else:                  
          alist[leftmark],alist[rightmark]=alist[rightmark],alist[leftmark] 

    alist[first],alist[rightmark]= alist[rightmark],alist[first]
    return rightmark

alist = [54,26,93,17,77,31,44,55,20]
quickSort(alist)
print(alist)

>>>[17, 20, 26, 31, 44, 54, 55, 77, 93]

Answer 3

I fixed the example on the site. It works now. @rollietikes had the correct solution. It appears that the editor "ate" the < and continued to consume characters thinking it was an html tag. This was a bug that we fixed months ago, but I should have rebuilt this book.

Brad