On Sat, Apr 26, 2014 at 11:43 PM, Philipp A. email@example.com wrote:
sure it works if `eggs` has a `__iadd__` method. why shouldn’t it use the outer local?
1) Operator precedence gets in the way. (Easily fixed.)
lambda: eggs += lay_eggs()
SyntaxError: can't assign to lambda
2) Assignment is a statement, so you can't do it in a lambda.
lambda: (eggs += lay_eggs())
SyntaxError: invalid syntax
3) Assignment makes it local, so you'll get UnboundLocalError if you don't declare it nonlocal.
eggs += lay_eggs()
Traceback (most recent call last): File "<pyshell#5>", line 1, in <module> f() File "<pyshell#4>", line 2, in f eggs += lay_eggs() UnboundLocalError: local variable 'eggs' referenced before assignment
Hence my previous statement that you need to write the function out of line, which breaks the switch-ness of the block, and you definitely need to declare eggs nonlocal. Now, if eggs is a list, you can extend it with a method (which can be called in an expression), but if your switch block can only do expressions, it's pretty limited.