[kazinator]

No, I mean this:

  def f(x):
    g = lambda : x
    x = 2
    return g()

  f(42)

What is does f(42) return?

Holy fuck, I simply cannot just cut and paste the above into Python as-is, because of the "unexpected indent" which I added so that HN shows that as quote. It's complaining about an unexpected indent.

Kill. Me. Now.

Anywway:

  >>> def f(x):
  ...   g = lambda : x
  ...   x = 2
  ...   return g()
  ... 
  >>> f(42)
  2

So what it looks like is that there is only one x in the function, established by the parameter. This x is captured by the lambda, and is then reassigned the value 2. The lambda retrieves the 2.

For completeness we show that if x is not assignmed, g accesses f's argument value:

  >>> def f(x):
  ...    g = lambda : x
  ...    return g()
  ... 
  >>> f(42)
  42