Question

编写一个生成器函数reverse_iter，该函数接受可迭代的序列并以相反的顺序生成项，而无需使用内置函数或方法。但是，使用该功能后，原始列表应保持不变。输出示例如下：

   it = reverse_iter(nums)
    next(it) == 4
True
    next(it)
3
    next(it)
2
    next(it)
1

请注意，即使将列表更改为元组，以上内容也应起作用。我不知道如何不使用诸如reverse（）或reversed（）之类的方法。也许利用-1切片？有任何想法吗？

Answer 1

def reverse_iter(nums): # A generator function
    idx = len(nums) - 1
    while idx > -1:
        yield nums[idx]
        idx -=1 

nums = [1,2,3,4]
print('before: ',*nums)
get = reverse_iter(nums)  # get is a generator object

print('manually')
# Iterating over the generator object using next
print(get.__next__()) # In Python 3+ , print(get.__next__())
print(get.__next__())
print(get.__next__())
print(get.__next__())

#print(get.next()) #now you will get StopIteration
#print(next(get,'traversing complete')) #to avoid the StopIteration exception


# printing all items in list in reverse 
print('\nusing for loop')
get = reverse_iter(nums)  # get is a generator object
for i in range(len(nums)):
    print(get.__next__())

print('after: ',*nums)

接受可重复的序列，然后以相反的顺序返回

1 个答案: