类型错误：“ generator”对象在python中不可下标

Question

def activity_select(i):
    list(i)
    i.sort(key=lambda x: x[2])
    n = len(i)                        # set n to length of i 
    solution = []
    print("Following activities are selected ")
    j = 0                             # first activity always selected
    solution.append(i[j][0])
    for k in range(n):                # loop through remainder of activities
        if i[k][1] >= i[k][2]:        # if activity has greater start time
            solution.append(i[k][0]) #
            j = k
            return solution

file = open('act.txt')
st = []
sn = 1
for line in file:
    l = line.rstrip()
    if '' not in l and len(st) > 0:
        print("Set", sn)
        solution = activity_select(st)
        print("Number of activities selected = ", len(solution))
        print("Activities: ", *solution)
        sn += 1
        st = []
else:
            st.append((int(i) for i in l.split()))
if len(st) > 0:
    print("Set ", sn)
    sol = activity_select(st)
    print("Number of activities selected = ", len(sol))
    print("Activities: ", *solution)

However I am getting the following errors

line 27, in <module>
    sol = activity_select(st)
line 9, in activity_select
    sol.append(v[i][0])
TypeError: 'generator' object is not subscriptable 

Is this related to the st variable? Or is it something else?

Answer 1

I see a couple obvious errors here:

1. You converted your i argument to a list and didn't assign it back to i , so if it's not a list , the function is broken from the start. Use i = list(i) to replace i with the result of listifying
2. You call st.append((int(i) for i in l.split())) which is calling append with a generator (created via a generator expression). If it's supposed to be a list , use brackets, not parens: st.append([int(i) for i in l.split()]) . If each result should be added separately, use extend instead: st.extend(int(i) for i in l.split())

Problem #2 is almost certainly the source of your current error, but fixing #1 is important for making your code usable with non-lists (and to avoid having it mutate the caller's copy of the list even when it works).

Answer 2

It is hard to debug your code seeing that you are reading of a file we do not have. My guess would be you are trying slice a generator, a quick glance shows that you have a generator expression here:

st.append((int(i) for i in l.split()))

Try changing it to st.append([int(i) for i in l.split()]) to get a nested list.

Answer 3

Basically the problem with your code is:

st.append((int(i) for i in l.split()))

because you're appending a generator with is un-indexable, un-sliceable , un-subscriptable , so use a list comprehension which is indexable, sliceable, subscriptable.

So instead of:

st.append((int(i) for i in l.split()))

Do:

st.append([int(i) for i in l.split()])