Constant folding in Python: think about why the bytecodes generated for f() and g() are different

constfold.rst

>>> import dis
>>> def f(x):
...     return 1+2+3+4+x
...
>>> f(5)
15
>>> dis.dis(f)
  2           0 LOAD_CONST               7 (10)
              3 LOAD_FAST                0 (x)
              6 BINARY_ADD
              7 RETURN_VALUE
>>> def g(x):
...     return x+1+2+3+4
...
>>> dis.dis(g)
  2           0 LOAD_FAST                0 (x)
              3 LOAD_CONST               1 (1)
              6 BINARY_ADD
              7 LOAD_CONST               2 (2)
             10 BINARY_ADD
             11 LOAD_CONST               3 (3)
             14 BINARY_ADD
             15 LOAD_CONST               4 (4)
             18 BINARY_ADD
             19 RETURN_VALUE