Exec () and the scope of variables

Question

I am sure that they asked and answered about this, but I could not find it specifically:

I just pick Python and I don't understand the problem with variable variable .

I simplified the problem as follows:

Case 1:

def lev1():
   exec("aaa=123")
   print("lev1:",aaa)

lev1()

Case 2:

def lev1():
   global aaa
   exec("aaa=123")
   print("lev1:",aaa)

lev1()

Case 3:

def lev1():
   exec("global aaa ; aaa=123")
   print("lev1:",aaa)

lev1()

• Case 1and Case 2have aaaundefined in the print instruction.
• Case 3works. Where aaadoes it really exist in Case 1and Case 2?
• Is there a way to access aaacase 1 without an announcement global?

Answer 1

From docs :

.. , locals() : . locals, exec().

, exec , - , Python , , .

exec uted , globals(). ( globals dict locals dict, exec dict , locals.)

def lev1():
   exec("aaa=123", globals())
   print("lev1:", aaa)

lev1()