def calculator(): expression = input("请输入算术表达式：") result = eval(expression) print("计算结果为：", result)

这段代码实现了一个简单的计算器功能，它会提示用户输入一个算术表达式，然后使用 Python 内置的 eval 函数计算表达式的值，并将结果输出给用户。需要注意的是，eval 函数可以执行任意的 Python 代码，因此在输入算术表达式时需要注意安全性问题。同时，如果用户输入的表达式不合法，比如除数为0，那么程序会抛出异常，需要在代码中加入异常处理逻辑。

相关问题

给下面的代码加上计算器窗口界面，要有显示器和键盘，并分析出生成后的代码信息处理流程： import math class Calculator: def init(self): self.result = 0 def add(self, num): self.result += num def sub(self, num): self.result -= num def mul(self, num): self.result *= num def div(self, num): if num == 0: print("Error: Cannot divide by zero!") else: self.result /= num def getResult(self): return self.result def clear(self): self.result = 0 def main(): calculator = Calculator() while True: print("Please select an operation:") print("1. Add") print("2. Subtract") print("3. Multiply") print("4. Divide") print("5. Clear") print("0. Exit") choice = int(input("Enter your choice: ")) if choice == 0: break elif choice == 1: num = float(input("Enter a number: ")) calculator.add(num) print("Result:", calculator.getResult()) elif choice == 2: num = float(input("Enter a number: ")) calculator.sub(num) print("Result:", calculator.getResult()) elif choice == 3: num = float(input("Enter a number: ")) calculator.mul(num) print("Result:", calculator.getResult()) elif choice == 4: num = float(input("Enter a number: ")) calculator.div(num) print("Result:", calculator.getResult()) elif choice == 5: calculator.clear() print("Result:", calculator.getResult()) else: print("Invalid choice. Please try again.") if name == 'main': main()

以下是加上计算器窗口界面后的代码，包括显示器和键盘界面的设计：

import math
import tkinter as tk

class Calculator:
    def __init__(self):
        self.result = 0

    def add(self, num):
        self.result += num

    def sub(self, num):
        self.result -= num

    def mul(self, num):
        self.result *= num

    def div(self, num):
        if num == 0:
            self.result = "Error: Cannot divide by zero!"
        else:
            self.result /= num

    def getResult(self):
        return self.result

    def clear(self):
        self.result = 0

class CalculatorGUI:
    def __init__(self, master):
        self.master = master
        master.title("Calculator")

        self.result_label = tk.Label(master, text="0", width=20, font=("Arial", 20))
        self.result_label.grid(row=0, column=0, columnspan=4)

        self.create_buttons()

        self.calculator = Calculator()

    def create_buttons(self):
        self.button1 = tk.Button(self.master, text="1", width=5, height=2, command=lambda: self.button_click(1))
        self.button2 = tk.Button(self.master, text="2", width=5, height=2, command=lambda: self.button_click(2))
        self.button3 = tk.Button(self.master, text="3", width=5, height=2, command=lambda: self.button_click(3))
        self.button4 = tk.Button(self.master, text="4", width=5, height=2, command=lambda: self.button_click(4))
        self.button5 = tk.Button(self.master, text="5", width=5, height=2, command=lambda: self.button_click(5))
        self.button6 = tk.Button(self.master, text="6", width=5, height=2, command=lambda: self.button_click(6))
        self.button7 = tk.Button(self.master, text="7", width=5, height=2, command=lambda: self.button_click(7))
        self.button8 = tk.Button(self.master, text="8", width=5, height=2, command=lambda: self.button_click(8))
        self.button9 = tk.Button(self.master, text="9", width=5, height=2, command=lambda: self.button_click(9))
        self.button0 = tk.Button(self.master, text="0", width=5, height=2, command=lambda: self.button_click(0))
        self.button_add = tk.Button(self.master, text="+", width=5, height=2, command=lambda: self.operation_click("+"))
        self.button_subtract = tk.Button(self.master, text="-", width=5, height=2, command=lambda: self.operation_click("-"))
        self.button_multiply = tk.Button(self.master, text="*", width=5, height=2, command=lambda: self.operation_click("*"))
        self.button_divide = tk.Button(self.master, text="/", width=5, height=2, command=lambda: self.operation_click("/"))
        self.button_clear = tk.Button(self.master, text="C", width=5, height=2, command=lambda: self.clear_click())
        self.button_equals = tk.Button(self.master, text="=", width=5, height=2, command=lambda: self.equals_click())

        self.button1.grid(row=3, column=0)
        self.button2.grid(row=3, column=1)
        self.button3.grid(row=3, column=2)
        self.button_add.grid(row=3, column=3)

        self.button4.grid(row=2, column=0)
        self.button5.grid(row=2, column=1)
        self.button6.grid(row=2, column=2)
        self.button_subtract.grid(row=2, column=3)

        self.button7.grid(row=1, column=0)
        self.button8.grid(row=1, column=1)
        self.button9.grid(row=1, column=2)
        self.button_multiply.grid(row=1, column=3)

        self.button_clear.grid(row=4, column=0)
        self.button0.grid(row=4, column=1)
        self.button_equals.grid(row=4, column=2)
        self.button_divide.grid(row=4, column=3)

    def button_click(self, number):
        current = self.result_label.cget("text")
        if current == "0":
            self.result_label.config(text=str(number))
        else:
            self.result_label.config(text=current + str(number))

    def operation_click(self, operation):
        current = self.result_label.cget("text")
        self.calculator.result = float(current)
        self.operation = operation
        self.result_label.config(text="0")

    def clear_click(self):
        self.calculator.clear()
        self.result_label.config(text="0")

    def equals_click(self):
        current = self.result_label.cget("text")
        self.calculator.result = float(current)
        if self.operation == "+":
            self.calculator.add(self.calculator.getResult())
        elif self.operation == "-":
            self.calculator.sub(self.calculator.getResult())
        elif self.operation == "*":
            self.calculator.mul(self.calculator.getResult())
        elif self.operation == "/":
            self.calculator.div(self.calculator.getResult())
        self.result_label.config(text=str(self.calculator.getResult()))

if __name__ == '__main__':
    root = tk.Tk()
    calculator_gui = CalculatorGUI(root)
    root.mainloop()

这个代码为用户提供了一个计算器界面，包括数字键、运算符键、清除键、等于键和显示器。当用户点击数字键时，数字将添加到显示器上。当用户点击运算符键时，当前数字将被存储并清除显示器。当用户点击等于键时，计算器将执行相应的操作并将结果显示在显示器上。如果用户点击清除键，那么计算器的结果将被重置为零。整个程序的控制流程是由按钮的事件处理程序控制的，这些事件处理程序与 Calculator 类中定义的方法相对应。

使用python实现一个http服务器，该服务器具有以下功能： 支持时间查询 支持算术表达式运算 支持天气查询

在Python中，我们可以使用内置的`http.server`模块来快速搭建一个基础的HTTP服务器，然后通过一些额外的库来扩展其功能。这里我们将分别介绍如何实现三个功能：

1. 时间查询：

from http.server import BaseHTTPRequestHandler, HTTPServer
import datetime

class TimeHandler(BaseHTTPRequestHandler):
    def do_GET(self):
        if self.path == '/time':
            now = datetime.datetime.now().strftime('%Y-%m-%d %H:%M:%S')
            self.send_response(200)
            self.end_headers()
            self.wfile.write(now.encode())
        else:
            self.send_error(404)

def run_time_server(host='localhost', port=8000):
    server_address = (host, port)
    httpd = HTTPServer(server_address, TimeHandler)
    print(f"Starting time server on {host}:{port}")
    httpd.serve_forever()

run_time_server()

访问 `http://<your_host>:8000/time` 可获取当前时间。

2. 算术表达式运算：
为了支持数学计算，我们可以使用第三方库`flask`（一个更强大的Web框架）配合`eval()`函数，但要注意安全性问题。

from flask import Flask, request, jsonify

app = Flask(__name__)

@app.route('/calculator', methods=['POST'])
def calculator():
    expression = request.form.get('expression')
    try:
        result = str(eval(expression))
        return jsonify({"result": result})
    except Exception as e:
        return jsonify({"error": "Invalid expression"}), 400

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=8001)

访问 `http://<your_host>:8001/calculator?expression=<your_expression>` 来计算表达式。

3. 天气查询（假设使用openweathermap API）：
首先需要安装`requests`库，然后申请API key并替换下面代码中的`YOUR_API_KEY`。

import requests
from flask import Flask, jsonify

app = Flask(__name__)

API_KEY = 'YOUR_API_KEY'
BASE_URL = "http://api.openweathermap.org/data/2.5/weather"

def get_weather(city_name):
    params = {
        'q': city_name,
        'appid': API_KEY,
        'units': 'metric',
    }
    response = requests.get(BASE_URL, params=params)
    data = response.json()
    if data['cod'] != 200:
        return None
    return data

@app.route('/weather/<city>')
def weather(city):
    data = get_weather(city)
    if data:
        main = data['main']
        temp = main['temp']
        description = data['weather'][0]['description']
        return jsonify({'temperature': temp, 'description': description})
    else:
        return jsonify({'error': 'City not found'}), 404

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=8002)

访问 `http://<your_host>:8002/weather/<city_name>` 查询指定城市的天气。