python计算器功能

import re
import tkinter
import tkinter.messagebox

root = tkinter.Tk()
# 设置窗口大小和位置
root.geometry('300x270+400+100')
# 不允许改变窗口大小
root.resizable(False, False)
# 设置窗口标题
root.title('简易计算机'.center(25))

# 设置用来显示信息的文本框，并设置为只读
contentVar = tkinter.StringVar(root, '0')
contentEntry = tkinter.Entry(root, textvariable=contentVar)
contentEntry['state'] = 'readonly'
contentEntry.place(x=10, y=10, width=280, height=20)


# 按钮通用代码
def buttonClick(btn):
    content = contentVar.get()
    # 如果已有内容是以小数点开头的，前面加0
    if content.startswith('.'):
        content = '0' + content

    # 根据不同按钮作出相应的处理
    if btn in '0123456789':
        if content == '0':
            content = ''
        content += btn
    elif btn == '.':
        lastPart = re.split(r'\+|-|\*|/', content)[-1]
        if '.' in lastPart:
            tkinter.messagebox.showerror('错误', '小数点太多了')
            return
        else:
            content += btn
    elif btn == 'C':
        content = '0'
    elif btn == '=':
        try:
            # 对输入的表达式求值
            content = str(eval(content))
        except:
            tkinter.messagebox.showerror('错误', '表达式错误')
            return
    elif btn in operators or btn in operators1:
        if content.endswith(operators) or content.endswith(operators1):
            tkinter.messagebox.showerror('错误', '不允许存在连续运算符')
            return
        content += btn
    elif btn == 'Sqrt':
        n = content.split('.')
        if all(map(lambda x: x.isdigit(), n)):
            content = eval(content) ** 0.5
        else:
            tkinter.messagebox.showerror('错误', '表达式错误')
            return

    contentVar.set(content)


# 放置Clear按钮和“=”按钮
btnClear = tkinter.Button(root, text='C', command=lambda: buttonClick('C'))
btnClear.place(x=20, y=40, width=50, height=20)
btnCompute = tkinter.Button(root, text='=', command=lambda: buttonClick('='))
btnCompute.place(x=230, y=230, width=50, height=20)

# 放置10个数字、小数点和计算平方根的按钮
digits = list('7894561230.') + ['Sqrt']
index = 0
for row in range(4):
    for col in range(3):
        d = digits[index]
        index += 1
        btnDigit = tkinter.Button(root, text=d, command=lambda x=d: buttonClick(x))
        btnDigit.place(x=20 + col * 70, y=80 + row * 50, width=50, height=20)

# 放置运算符按钮
index = 0
operators1 = ('/', '**', '//')
for index, operator1 in enumerate(operators1):
    btnOperator = tkinter.Button(root, text=operator1, command=lambda x=operator1: buttonClick(x))
    btnOperator.place(x=230, y=80 + index * 50, width=50, height=20)

operators = ('+', '-', '*')
for index, operator in enumerate(operators):
    if operator == '+' or operator == '-' or operator == '*':
        btnOperator = tkinter.Button(root, text=operator, command=lambda x=operator: buttonClick(x))
        btnOperator.place(x=90 + index * 70, y=40, width=50, height=20)

root.mainloop()