时间：2022-06-21 10:00:51 | 栏目：Python代码 | 点击：次
大家好啊！又是我TUSTer_! python里有自带的库math，cmath,和函数pow来开根号。下边让我带你了解他们吧！记得一键三连！
使用math库里的sqr()函数，在math库里边有很多数学函数，如三角函数sin（），pi-π等等：
import math
print(math.sqr(4))
输出结果：2Epsilon = 10e-16
def fab_h(x):
'''
求实数的绝对值
:param x: R
'''
if x >= 0:
return x
else:
return x * -1
def sqrt_h(x, n=2.0):
'''
n倍根号下x
牛顿迭代法
'''
val = x
last = 0.0
if n == 2.0:
while (fab_h(val - last) > Epsilon):
last = val
val = (val + x / val) / 2
return val
while (fab_h(val - last) > Epsilon):
last = val
val = ((n-1)*val + x / val**(n-1)) / n
return val
cmath多用于复数，负数的开平方。
# importing cmath library import cmath # using cmath.sqrt() method gfg = cmath.sqrt(3) print(gfg)
输出：
(1.7320508075688772+0j)
pow（x,y）的意思是返回x的y次方，如pow(x,2)就是返回x的平方，就是x^2,
#!/usr/bin/python # -*- coding: UTF-8 -*- import math # 导入 math 模块 print "math.pow(100, 2) : ", math.pow(100, 2) # 使用内置，查看输出结果区别 print "pow(100, 2) : ", pow(100, 2) print "math.pow(100, -2) : ", math.pow(100, -2) print "math.pow(2, 4) : ", math.pow(2, 4)
输出：
math.pow(100, 2) : 10000.0
pow(100, 2) : 10000
math.pow(100, -2) : 0.0001
math.pow(2, 4) : 16.0
math.pow(3, 0) : 1.0
import time
import math
import numpy as np
def timeit1():
s = time.time()
for i in range(750000):
z=i**.5
print ("Took %f seconds" % (time.time() - s))
def timeit2(arg=math.sqrt):
s = time.time()
for i in range(750000):
z=arg(i)
print ("Took %f seconds" % (time.time() - s))
def timeit3(arg=np.sqrt):
s = time.time()
for i in range(750000):
z=arg(i)
print ("Took %f seconds" % (time.time() - s))
def timeit4():
s = time.time()
for i in range(750000):
z=math.pow(i,.5)
print ("Took %f seconds" % (time.time() - s))
timeit1()
timeit2()
timeit3()
timeit4()
Took 0.152364 seconds
Took 0.061580 seconds
Took 1.016529 seconds
Took 0.215403 seconds