Removing coordinates from list on python

This question already has an answer here:

How to remove items from a list while iterating? 18 answers

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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 (eg sets and dicts).

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

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您可以使用列表理解进行过滤：

>>> coords =  [(1, 2), (5, 6), (-1, -2), (1, -2)]
>>> [coord for coord in coords
...  if not any(number < 0 for number in coord)]
[(1, 2), (5, 6)]

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