带tkin的Python3计算器

Question

我已经编程很久了。直到最近，我才决定尝试一下python（我应该用C来学习，因为我在学校学习，但我不喜欢windows。说来话长）

不管怎样，我在这个网站上，它显示了一个计算器的来源。我拿着它，把它放在PyCharm里，开始学习。当我完成时，我已经显著地改变了来源。我添加了键盘绑定并减少了其中的大量冗余代码。在

我的问题很简单，从python标准的角度来看，我编写的代码是否高效？在

# -*-coding: utf-8-*-
# !/usr/bin/python3.5

from tkinter import Tk, Button, Entry, END
import math

class Calc:
    def getandreplace(self):  # replace x, + and % to symbols that can be used in calculations
        # we wont re write this to the text box until we are done with calculations

        self.txt = self.e.get() # Get value from text box and assign it to the global txt var
        self.txt = self.txt.replace('÷', '/')
        self.txt = self.txt.replace('x', '*')
        self.txt = self.txt.replace('%', '/100')

    def evaluation(self, specfunc):  # Evaluate the items in the text box for calculation specfunc = eq, sqroot or power
        self.getandreplace()
        try:
            self.txt = eval(str(self.txt))  # evaluate the expression using the eval function
        except SyntaxError:
            self.displayinvalid()
        else:
            if any([specfunc == 'sqroot', specfunc == 'power']):  # Square Root and Power are special
                self.txt = self.evalspecialfunctions(specfunc)

            self.refreshtext()

    def displayinvalid(self):
        self.e.delete(0, END)
        self.e.insert(0, 'Invalid Input!')

    def refreshtext(self):  # Delete current contents of textbox and replace with our completed evaluatioin
        self.e.delete(0, END)
        self.e.insert(0, self.txt)

    def evalspecialfunctions(self, specfunc):  # Calculate square root and power if specfunc is sqroot or power
        if specfunc == 'sqroot':
            return math.sqrt(float(self.txt))
        elif specfunc == 'power':
            return math.pow(float(self.txt), 2)

    def clearall(self): # AC button pressed on form or 'esc" pressed on keyboard
        self.e.delete(0, END)
        self.e.insert(0, '0')

    def clear1(self, event=None):
        # C button press on form or backspace press on keyboard event defined on keyboard press

        if event is None:
            self.txt = self.e.get()[:-1]  # Form backspace done by hand
        else:
            self.txt = self.getvalue()  # No need to manually delete when done from keyboard

            self.refreshtext()

    def action(self, argi: object):  # Number or operator button pressed on form and passed in as argi
        self.txt = self.getvalue()

        self.stripfirstchar()

        self.e.insert(END, argi)

    def keyaction(self, event=None):  # Key pressed on keyboard which defines event
        self.txt = self.getvalue()

        if event.char.isdigit():
            self.stripfirstchar()
        elif event.char in '/*-+%().':
            self.stripfirstchar()
        elif event.char == '\x08':
            self.clear1(event)
        elif event.char == '\x1b':
            self.clearall()
        elif event.char == '\r':
            self.evaluation('eq')
        else:
            self.displayinvalid()
            return 'break'

    def stripfirstchar(self):  # Strips leading 0 from text box with first key or button is pressed
        if self.txt[0] == '0':
            self.e.delete(0, 1)

    def getvalue(self):  # Returns value of the text box
        return self.e.get()

    def __init__(self, master):  # Constructor method
        self.txt = 'o'  # Global var to work with text box contents
        master.title('Calulator')
        master.geometry()
        self.e = Entry(master)
        self.e.grid(row=0, column=0, columnspan=6, pady=3)
        self.e.insert(0, '0')
        self.e.focus_set()  # Sets focus on the text box text area

        # Generating Buttons
        Button(master, text="=", width=10, command=lambda: self.evaluation('eq')).grid(row=4, column=4, columnspan=2)
        Button(master, text='AC', width=3, command=lambda: self.clearall()).grid(row=1, column=4)
        Button(master, text='C', width=3, command=lambda: self.clear1()).grid(row=1, column=5)
        Button(master, text="+", width=3, command=lambda: self.action('+')).grid(row=4, column=3)
        Button(master, text="x", width=3, command=lambda: self.action('x')).grid(row=2, column=3)
        Button(master, text="-", width=3, command=lambda: self.action('-')).grid(row=3, column=3)
        Button(master, text="÷", width=3, command=lambda: self.action('÷')).grid(row=1, column=3)
        Button(master, text="%", width=3, command=lambda: self.action('%')).grid(row=4, column=2)
        Button(master, text="7", width=3, command=lambda: self.action('7')).grid(row=1, column=0)
        Button(master, text="8", width=3, command=lambda: self.action('8')).grid(row=1, column=1)
        Button(master, text="9", width=3, command=lambda: self.action('9')).grid(row=1, column=2)
        Button(master, text="4", width=3, command=lambda: self.action('4')).grid(row=2, column=0)
        Button(master, text="5", width=3, command=lambda: self.action('5')).grid(row=2, column=1)
        Button(master, text="6", width=3, command=lambda: self.action('6')).grid(row=2, column=2)
        Button(master, text="1", width=3, command=lambda: self.action('1')).grid(row=3, column=0)
        Button(master, text="2", width=3, command=lambda: self.action('2')).grid(row=3, column=1)
        Button(master, text="3", width=3, command=lambda: self.action('3')).grid(row=3, column=2)
        Button(master, text="0", width=3, command=lambda: self.action('0')).grid(row=4, column=0)
        Button(master, text=".", width=3, command=lambda: self.action('.')).grid(row=4, column=1)
        Button(master, text="(", width=3, command=lambda: self.action('(')).grid(row=2, column=4)
        Button(master, text=")", width=3, command=lambda: self.action(')')).grid(row=2, column=5)
        Button(master, text="√", width=3, command=lambda: self.evaluation('sqroot')).grid(row=3, column=4)
        Button(master, text="x²", width=3, command=lambda: self.evaluation('power')).grid(row=3, column=5)

        # bind key strokes
        self.e.bind('<Key>', lambda evt: self.keyaction(evt))


# Main
root = Tk()
obj = Calc(root)  # object instantiated
root.mainloop()

我并不关心某些函数名和变量名的名称。我喜欢用描述性的名字，所以像self.e这样的名字会被称为自身文本框或者别的什么。所以这些东西都是我从网上找到的，没有改变过。在

Answer 1

不是真正的代码审查的地方，但我还是要做，因为我是铁杆拖延。在

良好的代码

首先，你的代码是可行的（我想），看起来不错。好代码是任何语言中的好代码。有些人痴迷于代码是Python式的，我可不是那种人。在

图形用户界面结构

GUI代码糟透了。它是重复的，冗长的，精巧的和丑陋的。这不是对你的代码的批评，而是对所有GUI代码的评论，似乎没有一个好的解决方案。我们通过将GUI代码与其他代码分离来管理这一点。对于这一点，有一些正式的方法，如模型-视图-控制器和诸如关注点分离之类的主体。关键是将你丑陋脆弱的GUI代码与你关心的真实代码完全分离，这样我们就可以试着忘掉它有多难看。在

您的实现将GUI与功能紧密地联系在一起。这是一个小问题，所以这不是很糟糕。然而，作为一个学习练习，你应该把它们分开，以“正确”的方式来做，从创建第二个类开始，然后将评估功能转移到另一个类中。在

评估

第二件大事是eval函数的使用。它非常优雅，将输入转换成python兼容的数学，然后让python给出答案。稍微不同一点，你是在接受用户输入，过滤它一点，然后直接执行它。我的安全背景让我很震惊。这不是这个程序的问题，你在本地执行，用户不能做任何他们不能正常做的事情。但是不要对在线代码做类似的事情。在

主

最后，像这样组合类和代码时的标准做法是将代码放在__main__条件后面。这允许您将代码导入其他地方进行测试等。下面的链接很好地解释了这一点：

• What does if __name__ == "__main__": do?