Question

我有这个功能：

def compute():
    if txtot.get() == "":
        ot = 0
    elif txtmed.get() == "":
        med = 0
    else:
        bon = 0

    total = ot+med+bon
    print ("",total)

当被叫时加注：

UnboundLocalError: local variable 'med' referenced before assignment

知道如何解决？

Answer 1

由于只会执行fn thing_that_uses_say_hello<G>(greeter: &G, name: &str) -> String where G: Greeting, { greeter.say_hello(name.into()) } trait Greeting { fn say_hello(&self, name: &str) -> String; } struct RealGreeting; impl Greeting for RealGreeting { fn say_hello(&self, name: &str) -> String { format!("Hello, {}", name) } } #[cfg(test)] mod test { use super::*; use std::cell::RefCell; struct MockGreeting<'a> { called_with: RefCell<Vec<String>>, value: &'a str, } impl<'a> MockGreeting<'a> { fn new(value: &'a str) -> Self { Self { value, called_with: Default::default(), } } } impl<'a> Greeting for MockGreeting<'a> { fn say_hello(&self, name: &str) -> String { self.called_with.borrow_mut().push(name.to_owned()); self.value.to_owned() } } #[test] fn test1() { let g = MockGreeting::new("Hello"); let r = thing_that_uses_say_hello(&g, "Tom"); assert_eq!("Hello", r); assert_eq!(&*g.called_with.borrow(), &["Tom".to_string()]); } }语句的一个分支，因此在分支的所有三个中未分配值的变量将始终无法存在if语句。

在这种情况下，您的输出将始终为if-elif-else，但通常您希望在if语句之前将变量初始化为某个值，并根据条件递增它们。

UnboundLocalError：赋值前引用的局部变量'med'

1 个答案: