为什么不能在python 3中的global / nonlocal / return语句中更改变量？

Question

In javascript I'm used to being able to var a=5 or return a=5 but in python if I try global a=5 , nonlocal a=5 or return a=5 I get an error. Is there a reason behind why you can't or am I just doing something wrong

Answer 1

In some languages it is common practice to stick an assignment inside of another statement. For example,

if a = 1 { ... }

the Python developers decided this is a source of bugs since it is too close to

if a == 1:

Therefore, they banned the nesting of assignments inside of other statements. Since

global a 

is a statement unto itself, an assignment inside of the statement is not allowed.