Why is lambda allowed as a key in a dict?

[Duncan Booth]

Iain King <iainking at gmail.com> wrote:

> Sort of tangenitally; is there any real difference between the outcome
> of the two following pieces of code?
> 
> a = lambda x: x+2
> 
> def a(x):
>     return x+2
> 

Disassemble it to see. The functions themselves have identical code 
bytes, the only difference is the name of the code objects (and that 
carries through to a difference in the function names).

>>> def f():
	a = lambda x: x+2
	def b(x):
		return x+2
	dis(a)
	dis(b)

	
>>> from dis import dis
>>> dis(f)
  2           0 LOAD_CONST               1 (<code object <lambda> at 
0119FDA0, file "<pyshell#10>", line 2>)
              3 MAKE_FUNCTION            0
              6 STORE_FAST               0 (a)

  3           9 LOAD_CONST               2 (<code object b at 0119FDE8, 
file "<pyshell#10>", line 3>)
             12 MAKE_FUNCTION            0
             15 STORE_FAST               1 (b)

  5          18 LOAD_GLOBAL              0 (dis)
             21 LOAD_FAST                0 (a)
             24 CALL_FUNCTION            1
             27 POP_TOP             

  6          28 LOAD_GLOBAL              0 (dis)
             31 LOAD_FAST                1 (b)
             34 CALL_FUNCTION            1
             37 POP_TOP             
             38 LOAD_CONST               0 (None)
             41 RETURN_VALUE        
>>> f()
  2           0 LOAD_FAST                0 (x)
              3 LOAD_CONST               0 (2)
              6 BINARY_ADD          
              7 RETURN_VALUE        
  4           0 LOAD_FAST                0 (x)
              3 LOAD_CONST               1 (2)
              6 BINARY_ADD          
              7 RETURN_VALUE        


-- 
Duncan Booth http://kupuguy.blogspot.com