Question

我目前正在开发计算器程序。我设法使验证代码起作用，因此条目小部件仅接收valid_input列表中的值。尽管我目前正在尝试阻止输入“ 5 ** 2”和“ 2 // 2”，但是有一种方法可以使用验证码或test_input函数使用户无法输入两个相同的运营商。这主要是关于除法和乘法运算符。

from tkinter import *
from tkinter import messagebox

def replace_text(text):
    display.delete(0, END)
    display.insert(0, text)

#Calculates the input in the display        
def calculate(event = None):
    equation = display.get()
    try:
        result = eval(equation)
        replace_text(result)
        print(result) #Just for reference 
        return True 
    except: 
        messagebox.showerror("Error", "Math Error", parent = root)

#This function dosen't allow the user to input invalid values    
def test_input(value, action):
    #list of inputs that is valid for the calculator to function
    valid_input = ["7", "8", "9", "+", "4", "5", "6", "-", "1", "2", "3", "*", "0", ".", "/"]
    if action == "1": #If an insertion is occuring in the entry
        return all(char in valid_input for char in value)
    # if action != 1, allow it
    return True

root = Tk() 
root.title("Calculator testing")

display = Entry(root, font=("Helvetica", 16), justify = "right", validate = "key")
display.configure(validatecommand = (display.register(test_input), "%S", "%d"))
display.insert(0, "")
display.grid(column = 0, row = 0, columnspan = 4, sticky = "NSWE", padx = 10, pady = 10)
display.bind("=", calculate)

#Equals button
button_equal = Button(root, font = ("Helvetica", 14), text = "=", command = 
calculate, bg = "#c0ded9")
button_equal.grid(column = 2, row = 1, columnspan = 2, sticky = "WE")

#All clear button 
button_clear = Button(root, font = ("Helvetica", 14), text = "AC", command = 
lambda: replace_text(""), bg = "#c0ded9")
button_clear.grid(column = 0, row = 1, columnspan = 2, sticky = "WE")

#Main Program       
root.mainloop()

Answer 1

在验证功能中，您可以拆分用于插入数字和插入运算符/点的逻辑。

由于您关心条目中已经存在的内容以及要插入字符的位置，因此应将更多信息传递给validatecommand。您需要的信息是（from this answer）：

# %i = index of char string to be inserted/deleted, or -1
# %s = value of entry prior to editing
# %S = the text string being inserted or deleted, if any

然后，您可以进行多项检查来禁止任何会插入两个运算符或一个接一个的运算符的事情：

def test_input(insert, content, index, action):
    #list of inputs that is valid for the calculator to function
    valid_numbers = ["7", "8", "9", "4", "5", "6", "1", "2", "3", "0"]
    valid_chars = ["+", "-", "*", ".", "/"]
    index = int(index)
    if action != "1": # Always allow if it's not an insert
        return True
    if insert in valid_numbers: # Always allow a number
        return True
    if insert in valid_chars: # If it's an operator or point do further checks
        if index==0: # Disallow if it's the first character
            return False
        if content[index-1] in valid_chars: # Disallow if the character before is an operator or point
            return False
        if index != len(content): # If you're not at the end
            if content[index] in valid_chars: # Disallow if the next character is an operator or point
                return False
        return True # Allow if it's none of the above
    else:
        return False # Disallow if the character is not a number, operator or point

使用

display.configure(validatecommand = (display.register(test_input), "%S", "%s", "%i", "%d"))

我忘记了这会弄乱答案的插入，因为我假设一次只能插入一个字符。您可以（至少）通过两种方式解决此问题：

您可以关闭用于插入答案的验证，并在插入后重新打开：

display.configure(validate='none')
display.insert(0, text)
display.configure(validate='key')

或者，由于答案始终都是数字，因此您可以更改验证命令中的第二个if以允许多个数字而不是一个数字：

if all(char in valid_numbers for char in insert):

使用tkinter条目验证防止用户两次输入相同的值

1 个答案: