第 4 步：让我们计算圆的面积。一个圆的面积是 πr 2 ，所以我们需要创建一个变量来存储这个值。
3.14 是 π 的值，半径是我们的直径除以 2，** 2 是如何在 Python 中对一个数字求平方！
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Your micro:bit is not set up for this program. Follow these steps to use your device with Codesters:
Your micro:bit has an old version of the Codesters binary file. Follow these steps to update the file on your micro:bit:
Warning: This will erase any existing program on your micro:bit.
Having trouble? Check out the micro:bit instructions to update your firmware.
Setting up your micro:bit
Calibrate your micro:bit by tilting it until all the LEDs are lit.
For a demonstration see the micro:bit calibration instructions.
Try the following steps to connect to your Micro:bit:
1. You may need to reload this page and try your program again.
2. Try disconnecting and reconnecting your Micro:bit. Then reload the page and run your program again.
3. If you are still having problems your Micro:bit may have an old firmware version that is incompatible with Codesters.
To update the firmware follow these Micro:bit instructions.
Are you already running a Codesters project in another tab or window?
Micro:bit can only connect to one web page at a time. Try stopping other Codesters projects or closing other tabs or windows that may be using your Micro:bit.
If that doesn't fix the problem try disconnecting your Micro:bit, reloading this page, and reconnecting your Micro:bit.
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