Implement a simple calculator desktop software based on Python + tkinter

Have you ever wondered if you could develop a desktop gadget? If the answer is "yes", then you have come to the right place! Today, we're going to use the tkinter library in Python to create a simple desktop calculator.

1. Why tkinter?

tkinter is Python's standard GUI library. It's very friendly for beginners as it offers a large number of pre-made parts such as buttons, text boxes, etc., which makes developing graphical user interfaces incredibly easy.

2. Start our calculator journey

First, introduce the necessary libraries:

import tkinter as tk
from tkinter import ttk           

Then, we create a class called SimpleCalculator, which inherits from tk. Tk。

class SimpleCalculator(tk.Tk):
    def __init__(self):
        super().__init__()

        self.title("简易计算器")  # 设置窗口标题
        self.geometry("300x250")  # 设置窗口大小           

Now let's add a method create_widgets to this class for adding and laying out the interface widgets:

def create_widgets(self):
    # 创建一个文本框，用于显示和输入数据
    self.entry = ttk.Entry(self, width=30)
    self.entry.grid(row=0, column=0, columnspan=4, pady=20)  # 定位文本框的位置

    self.create_buttons()  # 创建按钮           

Here's how we create a button. We define a list of the text of each button and its row and column positions in the grid layout:

def create_buttons(self):
    # 按钮及其位置的列表
    buttons = [
        ("7", 1, 0),
        ("8", 1, 1),
        ("9", 1, 2),
        ("+", 1, 3),
        ...
    ]

    for (text, row, col) in buttons:
        self.create_button(text, row, col)  # 创建每一个按钮           

For each button, we'll create it using create_button method and bind an event to it:

def create_button(self, text, row, col):
    # 创建按钮，并绑定button_click事件
    button = ttk.Button(self, text=text, width=7, command=lambda: self.button_click(text))
    button.grid(row=row, column=col, padx=5, pady=5)  # 定位按钮位置           

When the user clicks the button, button_click method is triggered:

def button_click(self, char):
    current = self.entry.get()  # 获取文本框当前的内容

    if char == "=":
        # 尝试计算表达式的结果
        try:
            result = eval(current)
            self.entry.delete(0, tk.END)  # 清空文本框
            self.entry.insert(0, str(result))  # 插入结果
        except:
            self.entry.delete(0, tk.END)  # 清空文本框
            self.entry.insert(0, "错误")  # 显示错误信息
    elif char == "C":
        self.entry.delete(0, tk.END)  # 清空文本框
    else:
        self.entry.insert(tk.END, char)  # 向文本框插入字符           

Finally, to start the calculator application, we create an instance of SimpleCalculator and start tkinter's event loop:

if __name__ == "__main__":
    app = SimpleCalculator()
    app.mainloop()           

3. Demo video + complete code

The demo video is below, due to space limitations, if you need the full code, get the address for free: https://mp.weixin.qq.com/s/_GffebF6RFddxBbaZlwfsw

epilogue

That's our easy calculator! Although it seems simple, it's a great place to start for beginners. You can add more features to this, such as support for more math operations, history, or skin switching. If you're interested in programming, I encourage you to keep exploring. Python and tkinter give you powerful tools and endless possibilities. Don't stop, keep exploring, learning and creating!