(i**2 for i in l)：

l 是创建生成器时闭包捕获的，i ** 2 是 f.next() 时计算的

***

(l[i] for i in range(2))：

闭包没有捕获任何变量，计算 l[i] 时从外部作用域获取 l

***

两个表达式对应的 opcode ，注意看 LOAD opcode

```
2 8 LOAD_NAME 1 (list)
10 LOAD_CONST 1 (<code object <genexpr> at 0x10256d3a0, file "<dis>", line 2>)
12 LOAD_CONST 2 ('<genexpr>')
14 MAKE_FUNCTION 0
16 LOAD_NAME 0 (l)
18 GET_ITER
20 CALL_FUNCTION 1
22 CALL_FUNCTION 1
24 POP_TOP

3 26 LOAD_NAME 1 (list)
28 LOAD_CONST 3 (<code object <genexpr> at 0x10256d450, file "<dis>", line 3>)
30 LOAD_CONST 2 ('<genexpr>')
32 MAKE_FUNCTION 0
34 LOAD_NAME 2 (range)
36 LOAD_CONST 4 (2)
38 CALL_FUNCTION 1
40 GET_ITER
42 CALL_FUNCTION 1
44 CALL_FUNCTION 1
46 POP_TOP
48 LOAD_CONST 5 (None)
50 RETURN_VALUE

Disassembly of <code object <genexpr> at 0x10256d3a0, file "<dis>", line 2>:
2 0 LOAD_FAST 0 (.0)
>> 2 FOR_ITER 14 (to 18)
4 STORE_FAST 1 (i)
6 LOAD_FAST 1 (i)
8 LOAD_CONST 0 (2)
10 BINARY_POWER
12 YIELD_VALUE
14 POP_TOP
16 JUMP_ABSOLUTE 2
>> 18 LOAD_CONST 1 (None)
20 RETURN_VALUE

Disassembly of <code object <genexpr> at 0x10256d450, file "<dis>", line 3>:
3 0 LOAD_FAST 0 (.0)
>> 2 FOR_ITER 14 (to 18)
4 STORE_FAST 1 (i)
6 LOAD_GLOBAL 0 (l)
8 LOAD_FAST 1 (i)
10 BINARY_SUBSCR
12 YIELD_VALUE
14 POP_TOP
16 JUMP_ABSOLUTE 2
>> 18 LOAD_CONST 0 (None)
20 RETURN_VALUE

```