Python计算器的麻烦

Question

我想为小学生(4-11岁的孩子)制作一个数学应用程序，我已经从制作计算器开始了。我正在关注一个YouTube视频，但它显示了一个错误。顺便说一句，我是用python 3.4.3编写的。

这是我的代码：

from tkinter import*

def iCalc(source, side):
    storeObj = Frame(source, borderwidth=4, bd=4,bg="pink")
    storeObj.pack(side=side, expand=YES, fill=BOTH)
    return storeObj

def button (source, side, text, command=None):
    storeObj = Button(source, text=text, command=command)
    storeObj.pack(side=side, expand=YES, fill=BOTH)
    return storeObj

class app(Frame):
    def __init__(self):
        Frame.__init__(self)
        self.option_add('*Font', 'arial 20 bold')
        self.pack(expand=YES, fill=BOTH)
        self.master.title('Calculator')


        display = StringVar()
        Entry(self, relief=RIDGE,
                textvariable=display,justify='right' ,bd=30,bg="pink").pack(side=TOP, expand=YES,
                                                                            fill=BOTH)
        for clearBut in (["CE"],["C"]):
            erase = iCalc(self, TOP)
            for ichar in clearBut:
                button(erase, LEFT, ichar,
                       lambda storeObj=display, q=ichar: storeObj.set(''))

        for NumBut in ("789 /" , "456*" , "123-", "0.+"):
            FunctionNum = iCalc(self, TOP)
            for iEquals in NumBut:
                button(FunctionNum, LEFT, iEquals,
                        lambda storeObj=display, q=iEquals: storeObj.set(storeObj.get() + q))

        EqualsButton = iCalc(self, TOP)
        for iEquals in "=":
            if iEquals == '=':
                btniEquals = button(EqualsButton, LEFT, iEquals)
                btniEquals.bind('<ButtonRelease-1>',
                                lambda e, s=self, storeObj=display: s.calc(storeObj), '+')
            else:
                btniEquals = button(EqualsButton, LEFT, iEquals,
                    lambda storeObj=display, s=' %s '%iEquals: storeObj.set(storeObj.get()+s))


            def calc(self, display):
                try:
                    display.set(eval(display.get()))
                except:
                    display.set("ERROR")



if __name__ == '__main__':
    app().mainloop()

这就是不断出现的错误：

Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Python34\lib\tkinter\__init__.py", line 1533, in __call__
    return self.func(*args)
  File "C:\Users\sony\Documents\Raeesa Calc.py", line 42, in <lambda>
    lambda e, s=self, storeObj=display: s.calc(storeObj), '+')
AttributeError: 'app' object has no attribute 'calc'

这些错误意味着什么？

Answer 1

%s是应用程序对象。您的应用程序类没有calc方法。该名称的唯一出现形式是在__init__中的for循环中。如果这被认为是一个类方法，你需要把它拉到适当的缩进级别:删除足够的空格，使它垂直地位于"def init“下面。

另外，你想用这段代码做什么？

 for iEquals in "=":
     if iEquals == '=':

for循环在迭代集中恰好有一个值，它必须是一个等号。为什么你有一个让遍历一个常量项目的，然后测试它是否就是你所拥有的？一行简单的代码将会做同样的事情：

iEquals = '='

Answer 2

我已经解决了你这里的一些问题。在某种程度上，你不习惯于标记，但你肯定有一些错误。请看我的评论：

import ast
# Honestly you should do `import tkinter as tk`,
# but it's not that bad.
from tkinter import *

# this should be named something different,
# maybe something like `wrap_widget`. Also note
# snake_casing instead of camelCasing. Python avoids
# camelCasing, and uses StudlyCase for classes, and 
# snake_casing_for_everything_else.
def iCalc(source, side):
    storeObj = Frame(source, borderwidth=4, bd=4,bg="pink")
    storeObj.pack(side=side, expand=YES, fill=BOTH)
    return storeObj

def button(source, side, text, command=None):
    storeObj = Button(source, text=text, command=command)
    storeObj.pack(side=side, expand=YES, fill=BOTH)
    return storeObj

# Should be `App`. You could also just inherit from `tk.Tk`, which is
# a toplevel window.
class app(Frame):
    def __init__(self):
        Frame.__init__(self)
        self.option_add('*Font', 'arial 20 bold')
        self.pack(expand=YES, fill=BOTH)
        self.master.title('Calculator')

        display = StringVar()
        # Just further wrapped your line
        Entry(self,
              relief=RIDGE,
              textvariable=display,
              justify='right',
              bd=30,
              bg="pink").pack(side=TOP, expand=YES, fill=BOTH)

        # There was no need for looping over single element lists.
        # Also `button_text` is a more accurate name.
        for button_text in ("CE", "C"):
            erase = iCalc(self, TOP)
            button(erase, LEFT, button_text,
                   lambda storeObj=display, q=button_text: storeObj.set(''))

        # row is a better name here, as you're looping over
        # rows of button (texts)
        for row in ("789 /" , "456*" , "123-", "0.+"):
            FunctionNum = iCalc(self, TOP)
            # renamed button_text here, too.
            for button_text in row:
                button(FunctionNum, LEFT, button_text,
                        lambda storeObj=display, q=button_text: storeObj.set(storeObj.get() + q))

        EqualsButton = iCalc(self, TOP)
        # as others have mentioned you really shouldn't loop over the single element string.
        # I'm assuming you plan to add other characters in here. If not,
        # get rid of the extra code!
        for iEquals in "=":
            if iEquals == '=':
                btniEquals = button(EqualsButton, LEFT, iEquals)
                btniEquals.bind('<ButtonRelease-1>',
                                lambda e, s=self, storeObj=display: s.calc(storeObj), '+')
            else:
                btniEquals = button(EqualsButton, LEFT, iEquals,
                    lambda storeObj=display, s=' %s '%iEquals: storeObj.set(storeObj.get()+s))

    # This was indented *way* too much. That's why it wasn't defined.
    def calc(self, display):
        try:
            # I uses `ast.literal_eval`, as there are less security risks.
            # And for maths, there's really no reason to need anything else.
            display.set(ast.literal_eval(display.get()))
        except:
            display.set("ERROR")


if __name__ == '__main__':
    app().mainloop()