python基础--零散知识点

假设一个列表的存有 数量很大的元素,但是在每一次运行时,通常只调用前面几个元素,这时为了优化,可以采用生成器.

isList = [x * x for x in range(10)]
print(isList)  # 结果[0, 1, 4, 9, 16, 25, 36, 49, 64, 81]

isGenerator = (x * x for x in range(10))
print(isGenerator)  # 这里显示的结果是生成器的地址<generator object <genexpr> at 0x0000028E39D79938>

print("result :  %d " % next(isGenerator))  # result :  0
print("result :  %d " % next(isGenerator))  # result :  1
print("result :  %d " % next(isGenerator))  # result :  4

for i in isGenerator:
    print(i)  # 依次是 9, 16, 25, 36, 49, 64, 81


for it in isGenerator:
    print("this time :  %d" % it)  # 结果为空,这时如果继续调用next(isGenerator),会报StopIteration(因为越界).