反復中に Python リストから要素を削除すると予期しない結果が生じるのはなぜですか?

a = list(range(10))
remove = False
for b in a:
    if remove:
        a.remove(b)
    remove = not remove
print(a)

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]       <-  b = 0; remove? no
 ^
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]       <-  b = 1; remove? yes
    ^
[0, 2, 3, 4, 5, 6, 7, 8, 9]          <-  b = 3; remove? no
       ^
[0, 2, 3, 4, 5, 6, 7, 8, 9]          <-  b = 4; remove? yes
          ^
[0, 2, 3, 5, 6, 7, 8, 9]             <-  b = 6; remove? no
             ^
[0, 2, 3, 5, 6, 7, 8, 9]             <-  b = 7; remove? yes
                ^
[0, 2, 3, 5, 6, 8, 9]                <-  b = 9; remove? no
                   ^