从python上的列表中删除坐标 [英] Removing coordinates from list on python

问题描述

我已经在Python中创建了一个充满坐标"的列表:L1 = [(1,2,2，(5,6)，(-1，-2)，(1，-2)等.]

I have created a list full of "coordinates" in Python: L1 = [(1,2), (5,6), (-1,-2), (1,-2), etc..].

如果我想删除列表中所有包含负数的项目，我该怎么做?

If I wanted to remove all items in the list which contained negative numbers, how would I do this?

我尝试过:

for (a,b) in L1:
  if a < 0 or b < 0:
    L1.remove(a,b)

但是它不起作用.非常感谢您的帮助.

But it isn't working. Would very much appreciate any help.

杰克

推荐答案

在迭代过程中无法更改某些内容.结果很奇怪，违反直觉，几乎从来没有想要的结果.实际上，许多集合都明确禁止这样做(例如，集合和字典).

You cannot change something while you're iterating it. The results are weird and counter-intuitive, and nearly never what you want. In fact, many collections explicitly disallow this (e.g. sets and dicts).

相反，遍历一个副本(对于a [:]中的e:...)，或者，而不是修改现有列表，对其进行过滤以获取包含所需项目的新列表([e for e in a如果 ...]).请注意，在许多情况下，您无需再次进行迭代即可进行过滤，只需将过滤与数据生成合并即可.

Instead, iterate over a copy (for e in a[:]: ...) or, instead of modifying an existing list, filter it to get a new list containing the items you want ([e for e in a if ...]). Note that in many cases, you don't have to iterate again to filter, just merge the filtering with the generation of the data.

L2 = []
for (a,b) in L1:
  if a >= 0 and b >= 0:
    L2.append((a,b))

L1 = L2
print L1

这篇关于从python上的列表中删除坐标的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！