Question: I'm trying to build a list of the first ten factorials 

```
[1,1,2,6,24,120,720,5040,40320,362880]

```

using only list comprehension. Is that possible?

I don't know generators or `lambda`.

Here's my attempt, but I absolutely know why it's wrong:

```
lst = [1] + [i for i in range(1,10)]
lst[1:10] = [lst[i-1] * i for i in range(1,10)]
print(lst)

```

Answer: 
Just for fun:

One-liner mega-hack using list comprehension and an auxililary accumulator (the resulting list itself) to reuse previously computed value

```
s=[];  s=[s[-1] for x in range(1,10) if not s.append(x*s[-1] if s else 1)]

```

result:

```
[1, 2, 6, 24, 120, 720, 5040, 40320, 362880]

```

note: The `math.factorial` answer is the way when elements are random. Here it's faster because we can reuse previous results.

There's also another drawback: the need to store all elements in a `list` because python does not allow `if` and assignment like C does. So we have to append to a list and negate the `None` it returns so `if` test is `True`

As I said: fun, but still a hack.
Your attempt does not work because the list comprehension works element-wise, you cannot refer to `lst[i-1]` like that. There is a `factorial` function in `math` module, however, since you mentioned generators, you can use one like this

```
def mygenerator():
    total = 1
    current = 1
    while True:
        total *= current
        yield total
        current += 1

factorial = mygenerator()
output = [next(factorial) for i in range(10)]

```