#generator.py

def sqrs(nums_list):
    for num in nums_list:
        yield num**2         # quits at first yield?  NO
        #print("in loop")    # yes, all iterations happen
    print("Does happen")


sqr_nums = sqrs([1,2,3,4,5])   #sqr_nums is the generator
# values of a generator not stored in memory

print(next(sqr_nums))  #first one
print(next(sqr_nums))  #second
for i in sqr_nums:   #the rest
    print(i)
    
#print(next(sqr_nums))   #error. no more. StopIteration error


more_nums = (x**2 for x in [10,20,30,40,50])  #parens make it a generator, not a list comprehension
print(more_nums)   #"generator object"
#print(list(more_nums))   #convert to list, but then no more.
print(next(more_nums))
for i in more_nums:   #the rest
    print(i)