这段代码之所以有效,是因为循环将来迭代的所有项的索引都没有改变。但是在删除的值之后,值的重复上移使得这种技术对于长列表来说效率很低。这段代码的可视化执行在autbor.com/iteratebackwards1进行。你可以在图 8-3 中看到向前迭代和向后迭代的区别。 图8-3:向前(左)和向后(右)迭代时从列表中删除偶数 类似地,
>>> for i in range(len(someInts) - 1, -1, -1): ... if someInts[i] % 2 == 0: ... someInts.append(someInts[i]) ... >>> someInts [1, 7, 4, 5, 4] 这段代码的可视化执行在autbor.com/iteratebackwards2进行。通过向后迭代,我们可以在列表中添加或删除条目。但是这可能很难...
while chunk: next = chunk.pre # this iterates backwards, to go forwards use `next = chunk.post` chunk.pre = None chunk.post = None chunk.container = None chunk = next 1. 2. 3. 4. 5. 6. 7. 我还注意到,除非您希望外部代码包含对早期Chunk的引用,否则您可能根本不需要使用droprefs。在...
>>>someInts = [1,7,4,5]>>>foriinrange(len(someInts) -1, -1, -1):...ifsomeInts[i] %2==0:...someInts.append(someInts[i]) ...>>>someInts [1,7,4,5,4] 这段代码的可视化执行在autbor.com/iteratebackwards2进行。通过向后迭代,我们可以在列表中添加或删除条目。但是这可能很...
In Python, the range() function generates a sequence of numbers, often used in loops for iteration. By default, it creates numbers starting from 0 up to but not including a specified stop value. You can also reverse the sequence with reversed(). If you need to count backwards, then you...
# The 3rd argument of range means we iterate backwards, reducing the count # of i by 1 for i in range(n, -1, -1): heapify(nums, n, i) # Move the root of the max heap to the end of for i in range(n - 1, 0, -1): nums[i], nums[0] = nums[0], nums[i] heapify(...
The Iterator onject starts from the first element of the collection until all the elements are accessed. The iterator can only move forward without going backwards. 迭代器有两个基本的方法:iter() 和 next(). Iterator have two basic methods: iter() and next() ...
print("Range[-3:-1]:", t[-3:-1]) # Start with the 3rd last element, end just before the last element (upper bound is exclusive) print("Range[::-1]:", t[::-1]) # negative step with - print backwards # lists are similar to tuples... l = [11, 12, 13, "8", t] #...
>>> for i in range(len(someInts) - 1, -1, -1): ... if someInts[i] % 2 == 0: ... someInts.append(someInts[i]) ... >>> someInts [1, 7, 4, 5, 4] 1. 2. 3. 4. 5. 6. 7. 这段代码的可视化执行在autbor.com/iteratebackwards2进行。通过向后迭代,我们可以在列表...
# Propagate the error backwards through all the layers. # Use reversed to iterate backwards over the list of layers. for layer in reversed(layers): Y = activations.pop() # Get the activations of the last layer on the stack # Compute the error at the output layer. ...