Cannot change global variables in a function through an exec() statement?

Question

Why can I not change global variables from inside a function, using exec()? It works fine when the assignment statement is outside of exec(). Here is an example of my problem:

 >>> myvar = 'test' >>> def myfunc(): ...     global myvar ...     exec('myvar = "changed!"') ...     print(myvar) ...  >>> myfunc() test >>> print(myvar) test 

Answer 1

Per the docs, the exec statement takes two optional expressions, defaulting to globals() and locals(), and always performs changes (if any) in the locals() one.

So, just be more explicit/specific/precise...:

>>> def myfunc(): ...   exec('myvar="boooh!"', globals()) ...  >>> myfunc() >>> myvar 'boooh!' 

...and you'll be able to clobber global variables to your heart's contents.