"Ishwor" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
If you are curious about the detailed behavior of the CPython
implementation, the dis module is one aid. Compare
>>> def f1(l):
... l.extend([1])
... return l
...
>>> def f2(l):
... l += [1]
... return l
...
>>> import dis
>>> dis.dis(f1)
0 SET_LINENO 1
3 SET_LINENO 2
6 LOAD_FAST 0 (l)
9 LOAD_ATTR 1 (exten
12 LOAD_CONST 1 (1)
15 BUILD_LIST 1
18 CALL_FUNCTION 1
21 POP_TOP
22 SET_LINENO 3
25 LOAD_FAST 0 (l)
28 RETURN_VALUE
29 LOAD_CONST 0 (None)
32 RETURN_VALUE
>>> dis.dis(f2)
0 SET_LINENO 1
3 SET_LINENO 2
6 LOAD_FAST 0 (l)
9 LOAD_CONST 1 (1)
12 BUILD_LIST 1
15 INPLACE_ADD
16 STORE_FAST 0 (l)
19 SET_LINENO 3
22 LOAD_FAST 0 (l)
25 RETURN_VALUE
26 LOAD_CONST 0 (None)
29 RETURN_VALUE
Since INPLACE_ADD ends up calling .extend, the direct call should, on
average, be slightly faster. But the difference is comparable to the noise
of the variation in memory allocation time.
l.append(item) might be even faster than l.extend([item]), especially when
item is not a contant, since the unneeded list is not built.
Terry J. Reedy
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