我是电路小白，想接个按钮上去检测一下。

看到什么上拉下拉电阻，实在是不知道干啥的，谁能通俗的透彻的说一下理解。

下面是官方的说明，貌似是说可以编程控制 GPIO 默认输入高电平还是低电平的意思，设置默认值的感觉？

If you do not have the input pin connected to anything, it will 'float'. In other words, the value that is read in is undefined because it is not connected to anything until you press a button or switch. It will probably change value a lot as a result of receiving mains interference.

To get round this, we use a pull up or a pull down resistor. In this way, the default value of the input can be set. It is possible to have pull up/down resistors in hardware and using software. In hardware, a 10K resistor between the input channel and 3.3V (pull-up) or 0V (pull-down) is commonly used. The RPi.GPIO module allows you to configure the Broadcom SOC to do this in software:

GPIO.setup(channel, GPIO.IN, pull_up_down=GPIO.PUD_UP)

or

GPIO.setup(channel, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)