Question

我试图在循环中找到最后一次迭代，以便我可以跳过它。这并不理想我不知道，但我的问题是分开的。

我是python的新手，但如果我没有弄错的话，这个for循环就是解压变量letter。这使得for循环的第二次运行为空或在某种意义上被破坏。如果我的理解无论如何都是错误的，请随意评论或编辑。

this_iteration = 0
for [x, y, dx, dy, r], letter in letters_positions:
    last_iteration = this_iteration
    this_iteration += 1
this_iteration = 0

for [x, y, dx, dy, r], letter in letters_positions:
    if this_iteration == last_iteration:
        continue
    this_iteration += 1

我尝试在第二个for循环中未成功传递，但第二个for循环仍未运行。

for letter in letters_positions:

有没有办法让我在第二次循环中重新包装变量？

更新：这是CairoSVG，不是我自己的代码，但我会尽力发布更多上下文。 letters_positions取自svg文件。我的代码之前的重要两行是以下内容。

from .helpers import distance, normalize, point_angle, zip_letters

letters_positions = zip_letters(x, y, dx, dy, rotate, node.text)

原始的CairoSVG代码可以在github上找到。

https://github.com/Kozea/CairoSVG/blob/master/cairosvg/text.py

Answer 1

编辑（示例）：

this_iteration = 0
letters_positions = list(letters_positions)

for [x, y, dx, dy, r], letter in letters_positions:
    last_iteration = this_iteration
    this_iteration += 1
this_iteration = 0

for [x, y, dx, dy, r], letter in letters_positions:
    if this_iteration == last_iteration:
        continue
    this_iteration += 1

来自您发布的github link中的helpers.py：

# Incidentally, they say that this method returns a list with the current letter's positions.
# This isn't true - it is returning a generator.
# To return a list, the outermost parenthesis need to be replaced with square brackets,
#    or by simply adding list before the parenthesis
# i.e. [...] or list(...)
def zip_letters(xl, yl, dxl, dyl, rl, word):
    """Returns a list with the current letter's positions (x, y and rotation).
    E.g.: for letter 'L' with positions x = 10, y = 20 and rotation = 30:
    >>> [[10, 20, 30], 'L']
    Store the last value of each position and pop the first one in order to
    avoid setting an x,y or rotation value that have already been used.
    """
    # Notice the parenthesis below - this is a generator that gets exhausted after one iteration
    return (
        ([pl.pop(0) if pl else None for pl in (xl, yl, dxl, dyl, rl)], char)
        for char in word)

因此，在第一次迭代后将其清空。从中创建一个列表或其他一些数据结构letters_positions = list(letters_positions)，然后您可以多次循环它。

Answer 2

letters_positions是一个序列。如果您不想迭代最终元素，请迭代letters_positions[:-1]

编辑：如果您使用的是Python3，则可能需要先在list上致电letters_positions

在for循环中解包两次

2 个答案: