I think that looking at the generated bytecode is useful.
# Running with 'python -O'
>>> def f(x): x += 1
>>> dis.dis(f)
0 LOAD_FAST 0 (x)
3 LOAD_CONST 1 (1)
6 INPLACE_ADD
7 STORE_FAST 0 (x) ***
10 LOAD_CONST 0 (None)
13 RETURN_VALUE
>>> def g(x): x[0] += 1
>>> dis.dis(g)
0 LOAD_GLOBAL 0 (x)
3 LOAD_CONST 1 (0)
6 DUP_TOPX 2
9 BINARY_SUBSCR
10 LOAD_CONST 2 (1)
13 INPLACE_ADD
14 ROT_THREE
15 STORE_SUBSCR ***
16 LOAD_CONST 0 (None)
19 RETURN_VALUE
>>> def h(x): x.a += 1
>>> dis.dis(h)
0 LOAD_GLOBAL 0 (x)
3 DUP_TOP
4 LOAD_ATTR 1 (a)
7 LOAD_CONST 1 (1)
10 INPLACE_ADD
11 ROT_TWO
12 STORE_ATTR 1 (a) ***
15 LOAD_CONST 0 (None)
18 RETURN_VALUE
In each case, there's a STORE step to the inplace statement. In the case of the proposed
def j(x): x() += 1
what STORE instruction would you use?
>>> [opname for opname in dis.opname if opname.startswith("STORE")]
['STORE_SLICE+0', 'STORE_SLICE+1', 'STORE_SLICE+2', 'STORE_SLICE+3',
'STORE_SUBSCR', 'STORE_NAME', 'STORE_ATTR', 'STORE_GLOBAL', 'STORE_FAST',
'STORE_DEREF']
If you don't want one from the list, then you're looking at substantial
changes to Python.. (and STORE_DEREF probably doesn't do anything that's
relevant to this situation, though the name sure sounds promising,
doesn't it)
Jeff
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