小编use*_*274的帖子

如果我有一个列表,我想继续添加行,并按姓氏的字母顺序排序,怎么办呢？排序似乎只是通过字符串的第一个字母重新排列它们.

    line = "James Edward"   #Example line
    linesList.append("".join(line))   #Add it to a list
    linesList = sorted(linesList)   #Sort alphabetically

我收到了错误......

a = a + b
UnboundLocalError: local variable 'a' referenced before assignment

如果我在开始时分配了两个变量a和b,我不明白为什么会发生错误.

from tkinter import *

a = 10
b = 12
def stopProg(e):
    root.destroy()

def addNumbers(e):
    a = a + b
    label1.configure(text= str(a))

root=Tk()
button1=Button(root,text="Exit")
button1.pack()
button1.bind('<Button-1>',stopProg)
button2=Button(root,text="Add numbers")
button2.pack()
button2.bind('<Button-1>',addNumbers)
label1=Label(root,text="Amount")
label1.pack()

root.mainloop()