有人可以为我解释此代码吗？

Question

Can someone explain this piece of code for me, in simple terms.

prompts = ("Enter Strength Attribute, between 1 and 50: ", "Enter Skill Attribute, between 1 and 50: ") # I already now this so no need to explain it 

answers = [int(input(p)) for p in prompts]
if not all(0 < a <=50 for a in answers):
    # other code here

Is it a generator?

And how does it work?

Thanks in advance for any answers.

Answer 1

You have a list comprehension and a generator expression.

The list comprehension is:

[int(input(p)) for p in prompts]

and produces a list of integers from a list of prompts, asking the user for a series of numeric values.

It could also be expressed as:

answers = []
for p in prompts:
    result = int(input(p))
    answers.append(result)

Next is:

(0 < a <=50 for a in answers)

which is the generator expression. It tests if each of the numbers is a value between 0 (exclusive) and 50 (inclusive).

The all() function will loop over the generator expression one result at a time, and will return False the moment one of those results is False , or True when it exhausts the generator results and no False values were found.

You could replace the if all(...) test with:

result = True
for a in answers:
    if not 0 < a <= 50:
        result = False
        break

if result:

This would achieve the same effect; loop over answers one by one, but stop looping early if any of the tests was False (not a number greater than 0 and smaller than or equal to 50).

Answer 2

answers = [int(input(p)) for p in prompts]

This is a list comprehension. It could be written as a for loop like this:

answers = []
for p in prompts:
    resp = int(input(p))
    answers.append(resp)

---

if not all(0 < a <=50 for a in answers):

This is a generator, wrapped in all (a built in function that returns whether all elements are true) You could write that as a function:

def all(answers):
    for a in answer:
        if not 0 < a <= 50:
            return False  # note this short-circuits, stopping the loop
    return True

Answer 3

It is a list comprehension.

The first line does exactly the same as:

answers=[]
for p in prompts:
   a=int(input(p))
   answers.append(a)

The part of the second line behind the if condition does exactly the same as:

for a in answers:
        if a <= 0 or a > 50:
                 return False
return True

Answer 4

for p in prompts

enumerates the prompts

int(input(p))

asks the user for an input, using the p as a prompt, then try to coerce the input as an int

answers = [...]

makes answers a list of all the inputs converted in ints (this is a comprehension list)

(0 < a <=50 for a in answers)

This is a generator. It creates an iterable containing the test 0 < a <=50 for each value in the answers list

if not all(...)

Tests all elements in the generator. if any one is false, do other code