计算任意精度的圆周率是个有趣的主题，得益于python的强大计算能力，我们在MicroPython中也可以轻松的计算pi的数值。
先输入下面的代码：
""" 文件：pi.py 说明：用MicroPython计算任意精度圆周率计算 作者：未知 版本： 时间： 修改：邵子扬 2016.5 v1.1 http://bbs.micro-python.com/forum.php """ import time
def pi(places=10): # 3 + 3*(1/24) + 3*(1/24)*(9/80) + 3*(1/24)*(9/80)*(25/168) # The numerators 1, 9, 25, ... are given by (2x + 1) ^ 2 # The denominators 24, 80, 168 are given by (16x^2 -24x + 8) extra = 8 one = 10 ** (places+extra) t, c, n, na, d, da = 3*one, 3*one, 1, 0, 0, 24
while t > 1: n, na, d, da = n+na, na+8, d+da, da+32 t = t * n // d c += t return c // (10 ** extra)
def pi_t(n=10): t1=time.ticks_us() t=pi(n) t2=time.ticks_us() print('elapsed: ', time.ticks_diff(t1,t2)/1000000, 's') return t
def pi2(n=10): r=6*(10**n)*1000 p=0 k=0 c=r//2 d=c//(2*k+1) while d>0: p=p+d k=k+1 k2=2*k c=c*(k2-1)//(4*k2) d=c//(k2+1) return p//1000
def pi2_t(n=10): t1=time.ticks_us() t=pi2(n) t2=time.ticks_us() print('elapsed: ', time.ticks_diff(t1,t2)/1000000, 's') return t
我们将它复制到STM32F7DISC中（STM32F7DISC已经下载了MicroPython固件），然后测试一下计算速度。（在其它MicroPython开发板上也可以进行这个测试）
MicroPython v1.8 on 2016-05-15; F7DISC with STM32F746 Type "help()" for more information. >>> import pi >>> npi=pi.pi_t(1000) elapsed: 0.221486 s >>> npi=pi.pi_t(2000) elapsed: 0.793141 s >>> npi=pi.pi_t(5000) elapsed: 4.981964 s >>> npi=pi.pi_t(10000) elapsed: 21.02012 s >>>
从运行结果可以看出，虽然不是很快，但是考虑到STM32的资源和性能，结果已经出乎预料了，毕竟计算函数还不到10行代码，没有做深度优化。最后打印出1000位的圆周率，大家可以和标准结果比较看看。
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