列表理解-是否是双循环？

Question

I am having the following issue:

# Neither this

trial1 = [[x for x in 10000 // 5**i] for i in range(1, 10)]

# nor this

trial2 = [x for i in range(1, 10) for x in 10000 // 5**i]

# work.

They both return: "int" object is not iterable, which is somehow confusing to me. Since i is an array (1,2,3,...,9) so must be the 10000 // 5**i formula. So which is the integer i can't iterate over?. I want trial to be a list containing all these values.

How is this so different?

trial = []
for i in range(1, k):
    trial.append(10000 // 5**i)

How does one go about formulating the list comprehension statement?

Answer 1

The comprehension equivalent of your working for loop would be:

[10000 // 5**i for i in range(1, 10)]

There are no double loops in that example, so there shouldn't be in the comprehension either.

Regarding your second question; i is not a list with values (0, 1, ... , 9) but it is a single integer out of that list.

Answer 2

The equivalent of

trial = []
for i in range(1, k):
    trial.append(n // 5**i)

is simply

trial = [10000 // 5**i for i in range(1, k)]

since you are simply calculating 10000 // 5**i for ever i in range(1, k)

Answer 3

for x in 10000 // 34**i or anything like that means iterating through a number , which doesn't make sense and results in an error.

You seem to be trying to append numbers to a list, which is easy:

trial = [10000 // 5**i for i in range(1, 5)]

Here you're basically saying:

1. Create a list ( [...] )
2. That consists of values, each of them is equal to 10000//5**i
3. Where i is every number from range(1, 5)