tkinter 创建可以输入复杂算式的计算器

之前写过 使用 vscode 借助 PyQt5 设计一个计算器，我们可以发现 PyQt5 有点繁琐，本文使用 tkinter 以尽可能少的代码实现一个计算器：

from tkinter import Tk, StringVar, ttk


class App(Tk):
    def __init__(self):
        super().__init__()
        self.result = StringVar()
        self.result_label = ttk.Label(self, textvariable=self.result,
                                      background='lightgreen', width=15)
        self.cal_frame = ttk.Frame(self, relief='solid')
        self.values = []
        self.names = ['123+', '456-', '789×', 'C./=']
        style = ttk.Style(self)
        style.configure("BW.TLabel", foreground="black", background="lightblue", font='Times 14')
        self.widgets = self.create_widgets(self.names)

    def create_button(self, key):
        widget = ttk.Label(self.cal_frame, text=key,
                           anchor='center',
                           width=5, relief='raise', style="BW.TLabel")
        widget.bind('<1>', lambda event: self.get_value(event, key))
        return widget

    def create_widgets(self, names):
        _widgets = [[self.create_button(key) for key in row] for row in names]
        return _widgets

    def layout(self):
        self.result_label.grid(row=0, column=0, sticky='nsew')
        self.cal_frame.grid(row=1, column=0, sticky='nsew')
        for m, row in enumerate(self.widgets):
            for n, widget in enumerate(row):
                widget.grid(row=m, column=n, sticky='we')

    def get_value(self, event, key):
        self.values.append(key)
        res = ''.join(self.values)
        self.result.set(res)
        if key == '=':
            res = res.replace('×', '*')[:-1]
            try:
                self.result.set(eval(res))
            except:
                self.result.set('Error!')
            finally:
                self.values = []
        elif key == 'C':
            self.result.set('')
            self.values = []
        

root = App()
root.layout()
root.columnconfigure(0, weight=1)
root.rowconfigure(0, weight=2)
root.rowconfigure(1, weight=2)
root.cal_frame.rowconfigure(0, weight=2)
root.cal_frame.rowconfigure(1, weight=2)
root.cal_frame.rowconfigure(2, weight=2)
root.cal_frame.rowconfigure(3, weight=2)
root.cal_frame.rowconfigure(4, weight=2)
root.cal_frame.columnconfigure(0, weight=1)
root.cal_frame.columnconfigure(1, weight=1)
root.cal_frame.columnconfigure(2, weight=1)
root.cal_frame.columnconfigure(3, weight=1)
root.cal_frame.columnconfigure(4, weight=1)
root.mainloop()

如果输入的算式有误，会报错，比如，输入如下错误的算式：

显示结果为：