本地變量引用之前，但我已經分配了它的值

Question

所以我正在寫一個程序，轉換貨幣爲學校項目。我嘗試使用盡可能多的循環和引用來使程序儘可能短。但我不斷收到錯誤

"UnboundLocalError: local variable 'v3' referenced before assignment".

這是代碼（注：我修剪它，所以它只是必要的部分）。

from tkinter import * 
root = Tk() 
btn1 = StringVar() 
btn2 = StringVar() 
VALUTE = [ #besedilo v gumbu, oznaka, tečaj 
    ("Evro", "evrov", 1), 
    ("Dolar", "dolarjev", 1.12005), 
    ("Funt", "funtov", 0.739868547), 
] 
v = v2 = v3 = v4 = 1 
def funkcija(): 
    n = int(entry1.get()) 
    X = btn1.get() 
    Y = btn2.get() 
    for text, mark, convert in VALUTE: 
     if v3 == X: 
      o = convert 
      E = mark 
     v3 = v3 + 1 
     if v4 == Y: 
      p = convert 
      F = mark 
     v4 = v4 + 1 
    m = pretvorba(o,p) 
    print("%s %s je %s %s." % (n, E, m, F)) 

def pretvorba(a,b): 
    Q = n/a*b 
    return Q 

for text, mark, convert in VALUTE: 
    gumb = Radiobutton(root, text=text, value = v, variable = btn1).grid(row = v+1, column=1, sticky=W) 
    v=v+1 

for text, mark, convert in VALUTE: 
    gumb = Radiobutton(root, text=text, value = v2, variable = btn2).grid(row = v2+6, column=1, sticky=W) 
    v2=v2+1 

entry1 = Entry(root) 
entry1.grid(row=1, column=1, sticky=W) 

go = Button(root, text="Izračun", fg="white", bg="black", command=funkcija) 
go.grid(row=10, columnspan=3) 

root.mainloop() 

Answer 1

看起來你叫v3 == X你在函數初始化funkcija() v3之前。你需要V3傳遞給函數funkcija(v3)或者將其定義爲一個全局變量global v3當你分配一個值來訪問該功能

Answer 2

在Python內部變量的函數，編譯器假定，除非另有規定，該變量是本地的。例如：

x = 42 
y = "this is a test" 

def foo(): 
    x = 1  # this is local, unrelated to the external defined one 
    print(y) # this is global 

如果你想改變一個全球性的，你需要明確告知的編譯器與global功能：

def bar(): 
    global x 
    x = 1  # this changes the global variable x 

Answer 3

行，所以我想通了。我在函數def funkcija()內定義了v3和v4。然後，我將X和Y轉換爲整數，並將其作爲n全局。事實證明，if循環沒有運行，因爲X和Y不是整數。

這裏的固定代碼：

v = v2 = 1 
def funkcija(): 
    v3 = v4 = 1 
    n = float(entry1.get()) 
    global n 
    X = int(btn1.get()) 
    Y = int(btn2.get()) 
    for text, mark, convert in VALUTE: 
     if v3 == X: 
      o = convert 
      E = mark 
     v3+=1 
     if v4 == Y: 
      p = convert 
      F = mark 
     v4+=1 
    m = pretvorba(o,p) 
    print("%s %s je %s %s." % (n, E, m, F)) 

def pretvorba(a,b): 
    Q = n/a*b 
    return Q