Python: python的简单表达式计算器
这是一个简单的表达式计算器, 不太懂用Tkinter写GUI, 参考了别人的代码
from __future__ import division
from Tkinter import Tk, Entry, Button, Label, mainloop
from tkFont import Font
def get_value ():
v = ''
try:
v = eval(text.get()) #use eval to calculate the vlaue of the text
except:
pass
if isinstance(v, (int, float, long)):
pass
else:
v = 'Error...'
label.config(text = v) #use config to change the text
top = Tk()
top.title("calculator")
ft = Font(family = 'Courier New', size = 12)
text = Entry(top, font = ft)
button = Button(top, text = 'Ok', command = get_value)
label = Label(text = '(+ - * / % **)', font = ft)
Enter = lambda x: x.keycode == 13 and get_value()
Key = lambda x: label.config(text = '(+ - * / % **)')
text.bind('<Key>', Enter) #when the key is enter, execute the function Enter
text.focus()
text.bind('<Button-1>', Key) #when click the left-key, execute the function Key
text.pack()
button.pack()
label.pack()
mainloop()
相关文档：
def Start(self):
if (self.conn == None) or (self.conn.State == 1):
self.conn = win32com.client.Dispatch(r'ADODB.Connection')
&n ......
type相关：
所有自定义类A
其实例，如 a = A()
使用type运算符返回的都是<type, 'instance'>
而基本类型
比如 b = 3
type(b)，结果是<type, 'int'>
python的type不像C++中的typeid那样，可以显示类名。
（注：对于没有virtual函数的类而言，typeid是编译时期的事情（也就是静态类型）；对于有virtual函 ......
对数据库的操作基本分为三步：
连接数据库
根据需要执行SQL语句，接受返回值
关闭连接
我们正常的数据库应该都离不开这三步，下来说说如何使用python中的MySQLdb模块进行这些操作：
首先，我们需要把MySQLdb引入到程序中
import MySQLdb
然后开始数据库操作
1.数据库连接
conn = MySQLdb. ......
threading — Higher-level threading interface
This module constructs higher-level threading interfaces on top of the lower level _thread module. See also the queue module.
The dummy_threading module is provided for situations where threading cannot be used because _thread is missing.
......
multiprocessing — Process-based “threading” interface
Introduction
multiprocessing is a package that supports spawning processes using an API similar to the threading module. The multiprocessing package offers both local and remote concurrency, effectively side-stepping the Glo ......
