In [14]: l=[1,2,3,4]

In [15]: for i in l:
print i
....:
....:
1
2
3
4

In [17]: l=[1,2,3,4]

In [18]: for i in l:
print i
if i < 3:
l.remove(i)
....:
....:
1
3
4


なんで2が出ないのですか？