鳕鱼天空

This is Mr Wang's Tech Blog.

python中math模块常用的方法整理

ceil:取大于等于x的最小的整数值,如果x是一个整数,则返回x

copysign:把y的正负号加到x前面,可以使用0

cos:求x的余弦,x必须是弧度

degrees:把x从弧度转换成角度

e:表示一个常量

exp:返回math.e,也就是2.71828的x次方

expm1:返回math.e的x(其值为2.71828)次方的值减1

fabs:返回x的绝对值

factorial:取x的阶乘的值

floor:取小于等于x的最大的整数值,如果x是一个整数,则返回自身

fmod:得到x/y的余数,其值是一个浮点数

frexp:返回一个元组(m,e),其计算方式为:x分别除0.5和1,得到一个值的范围

fsum:对迭代器里的每个元素进行求和操作

gcd:返回x和y的最大公约数

hypot:如果x是不是无穷大的数字,则返回True,否则返回False

isfinite:如果x是正无穷大或负无穷大,则返回True,否则返回False

isinf:如果x是正无穷大或负无穷大,则返回True,否则返回False

isnan:如果x不是数字True,否则返回False

ldexp:返回x*(2**i)的值

log:返回x的自然对数,默认以e为基数,base参数给定时,将x的对数返回给定的base,计算式为:log(x)/log(base)

log10:返回x的以10为底的对数

log1p:返回x+1的自然对数(基数为e)的值

log2:返回x的基2对数

modf:返回由x的小数部分和整数部分组成的元组

pi:数字常量,圆周率

pow:返回x的y次方,即x**y

radians:把角度x转换成弧度

sin:求x(x为弧度)的正弦值

sqrt:求x的平方根

tan:返回x(x为弧度)的正切值

trunc:返回x的整数部分

ceil

#取大于等于x的最小的整数值,如果x是一个整数,则返回x
ceil(x)
Return the ceiling of x as an int.
This is the smallest integral value >= x.
>>> math.ceil(4.01)
5
>>> math.ceil(4.99)
5
>>> math.ceil(-3.99)
-3
>>> math.ceil(-3.01)
-3

copysign

#把y的正负号加到x前面,可以使用0
copysign(x, y)
Return a float with the magnitude (absolute value) of x but the sign 
of y. On platforms that support signed zeros, copysign(1.0, -0.0) 
returns -1.0.
>>> math.copysign(2,3)
2.0
>>> math.copysign(2,-3)
-2.0
>>> math.copysign(3,8)
3.0
>>> math.copysign(3,-8)
-3.0

cos

#求x的余弦,x必须是弧度
cos(x)
Return the cosine of x (measured in radians).
#math.pi/4表示弧度,转换成角度为45度
>>> math.cos(math.pi/4)
0.7071067811865476
math.pi/3表示弧度,转换成角度为60度
>>> math.cos(math.pi/3)
0.5000000000000001
math.pi/6表示弧度,转换成角度为30度
>>> math.cos(math.pi/6)
0.8660254037844387

degrees

#把x从弧度转换成角度
degrees(x)
Convert angle x from radians to degrees.
>>> math.degrees(math.pi/4)
45.0
>>> math.degrees(math.pi)
180.0
>>> math.degrees(math.pi/6)
29.999999999999996
>>> math.degrees(math.pi/3)
59.99999999999999

e

#表示一个常量
>>> math.e
2.718281828459045

exp

#返回math.e,也就是2.71828的x次方
exp(x)
Return e raised to the power of x.
>>> math.exp(1)
2.718281828459045
>>> math.exp(2)
7.38905609893065
>>> math.exp(3)
20.085536923187668

expm1

#返回math.e的x(其值为2.71828)次方的值减1
expm1(x)
Return exp(x)-1.
This function avoids the loss of precision involved in the direct evaluation of exp(x)-1 for small x.
>>> math.expm1(1)
1.718281828459045
>>> math.expm1(2)
6.38905609893065
>>> math.expm1(3)
19.085536923187668

fabs

#返回x的绝对值
fabs(x)
Return the absolute value of the float x.
>>> math.fabs(-0.003)
0.003
>>> math.fabs(-110)
110.0
>>> math.fabs(100)
100.0

factorial

#取x的阶乘的值
factorial(x) -> Integral
Find x!. Raise a ValueError if x is negative or non-integral.
>>> math.factorial(1)
1
>>> math.factorial(2)
2
>>> math.factorial(3)
6
>>> math.factorial(5)
120
>>> math.factorial(10)
3628800

floor

#取小于等于x的最大的整数值,如果x是一个整数,则返回自身
floor(x)
Return the floor of x as an int.
This is the largest integral value <= x.
>>> math.floor(4.1)
4
>>> math.floor(4.999)
4
>>> math.floor(-4.999)
-5
>>> math.floor(-4.01)
-5

fmod

#得到x/y的余数,其值是一个浮点数
fmod(x, y)
Return fmod(x, y), according to platform C.  x % y may differ.
>>> math.fmod(20,3)
2.0
>>> math.fmod(20,7)
6.0

frexp

#返回一个元组(m,e),其计算方式为:x分别除0.5和1,得到一个值的范围,
#2**e的值在这个范围内,e取符合要求的最大整数值,然后x/(2**e),得到m的值
#如果x等于0,则m和e的值都为0,m的绝对值的范围为(0.5,1)之间,不包括0.5和1
frexp(x)
Return the mantissa and exponent of x, as pair (m, e).
m is a float and e is an int, such that x = m * 2.**e.
If x is 0, m and e are both 0.  Else 0.5 <= abs(m) < 1.0.
>>> math.frexp(10)
(0.625, 4)
>>> math.frexp(75)
(0.5859375, 7)
>>> math.frexp(-40)
(-0.625, 6)
>>> math.frexp(-100)
(-0.78125, 7)
>>> math.frexp(100)
(0.78125, 7)

fsum

#对迭代器里的每个元素进行求和操作
fsum(iterable)
Return an accurate floating point sum of values in the iterable.
Assumes IEEE-754 floating point arithmetic.
>>> math.fsum([1,2,3,4])
10.0
>>> math.fsum((1,2,3,4))
10.0
>>> math.fsum((-1,-2,-3,-4))
-10.0
>>> math.fsum([-1,-2,-3,-4])
-10.0

gcd

#返回x和y的最大公约数
gcd(x, y) -> int
greatest common divisor of x and y
>>> math.gcd(8,6)
2
>>> math.gcd(40,20)
20
>>> math.gcd(8,12)
4

hypot

#得到(x**2+y**2),平方的值
hypot(x, y)
Return the Euclidean distance, sqrt(x*x + y*y).
>>> math.hypot(3,4)
5.0
>>> math.hypot(6,8)
10.0

isfinite

#如果x是不是无穷大的数字,则返回True,否则返回False
isfinite(x) -> bool
Return True if x is neither an infinity nor a NaN, and False otherwise.
>>> math.isfinite(100)
True
>>> math.isfinite(0)
True
>>> math.isfinite(0.1)
True
>>> math.isfinite("a")
>>> math.isfinite(0.0001)
True

isinf

#如果x是正无穷大或负无穷大,则返回True,否则返回False
isinf(x) -> bool
Return True if x is a positive or negative infinity, and False otherwise.
>>> math.isinf(234)
False
>>> math.isinf(0.1)
False

isnan

#如果x不是数字True,否则返回False
isnan(x) -> bool
Return True if x is a NaN (not a number), and False otherwise.
>>> math.isnan(23)
False
>>> math.isnan(0.01)
False

ldexp

#返回x*(2**i)的值
ldexp(x, i)
Return x * (2**i).
>>> math.ldexp(5,5)
160.0
>>> math.ldexp(3,5)
96.0

log

#返回x的自然对数,默认以e为基数,base参数给定时,将x的对数返回给定的base,计算式为:log(x)/log(base)
log(x[, base])
Return the logarithm of x to the given base.
If the base not specified, returns the natural logarithm (base e) of x.
>>> math.log(10)
2.302585092994046
>>> math.log(11)
2.3978952727983707
>>> math.log(20)
2.995732273553991

log10

#返回x的以10为底的对数
log10(x)
Return the base 10 logarithm of x.
>>> math.log10(10)
1.0
>>> math.log10(100)
2.0
#即10的1.3次方的结果为20
>>> math.log10(20)
1.3010299956639813

log1p

#返回x+1的自然对数(基数为e)的值
log1p(x)
Return the natural logarithm of 1+x (base e).
The result is computed in a way which is accurate for x near zero.
>>> math.log(10)
2.302585092994046
>>> math.log1p(10)
2.3978952727983707
>>> math.log(11)
2.3978952727983707

log2

#返回x的基2对数
log2(x)
Return the base 2 logarithm of x.
>>> math.log2(32)
5.0
>>> math.log2(20)
4.321928094887363
>>> math.log2(16)
4.0

modf

#返回由x的小数部分和整数部分组成的元组
modf(x)
Return the fractional and integer parts of x.  Both results carry the sign
of x and are floats.
>>> math.modf(math.pi)
(0.14159265358979312, 3.0)
>>> math.modf(12.34)
(0.33999999999999986, 12.0)

pi

#数字常量,圆周率
>>> print(math.pi)
3.141592653589793

pow

#返回x的y次方,即x**y
pow(x, y)
Return x**y (x to the power of y).
>>> math.pow(3,4)
81.0
>>> 
>>> math.pow(2,7)
128.0

radians

#把角度x转换成弧度
radians(x)
Convert angle x from degrees to radians.
>>> math.radians(45)
0.7853981633974483
>>> math.radians(60)
1.0471975511965976

sin

#求x(x为弧度)的正弦值
sin(x)
Return the sine of x (measured in radians).
>>> math.sin(math.pi/4)
0.7071067811865475
>>> math.sin(math.pi/2)
1.0
>>> math.sin(math.pi/3)
0.8660254037844386

sqrt

#求x的平方根
sqrt(x)
Return the square root of x.
>>> math.sqrt(100)
10.0
>>> math.sqrt(16)
4.0
>>> math.sqrt(20)
4.47213595499958

tan

#返回x(x为弧度)的正切值
tan(x)
Return the tangent of x (measured in radians).
>>> math.tan(math.pi/4)
0.9999999999999999
>>> math.tan(math.pi/6)
0.5773502691896257
>>> math.tan(math.pi/3)
1.7320508075688767

trunc

#返回x的整数部分
trunc(x:Real) -> Integral
Truncates x to the nearest Integral toward 0. Uses the __trunc__ magic method.
>>> math.trunc(6.789)
6
>>> math.trunc(math.pi)
3
>>> math.trunc(2.567)
2

Ardino节电模式、自动休眠、按钮打开和关闭

#include <avr/sleep.h>
#include <avr/power.h>
//#include <avr/wdt.h>

#include <MsTimer2.h>

int pin = 13;

volatile int f_sleepButton = 0;
volatile int f_sleepTimer = 0;

void setup() {
  //Serial.begin(9600);
  //Serial.print("Welcome to use!\n");
  pinMode(pin, OUTPUT);
  pinMode(2, INPUT);

  MsTimer2::set(2000, sleepTimer);        // 中断设置函数,每 2000ms 进入一次中断
  MsTimer2::start();

  sleepNow();
}

void loop() {
  if (digitalRead(2)) {
    //sleepNow();
    f_sleepButton++;
    clearsleepTimer();
    delay(50);
  }
  if (f_sleepButton == 24) {  // 长按1.2秒关机
    sleepNow();
  }
  if (f_sleepTimer == 10) { // 延时没有操作关机
    sleepNow();
  }
}

void sleepTimer() {
  f_sleepTimer++;
}

void sleepNow()         // here we put the arduino to sleep
{
  //detachInterrupt(0);
  digitalWrite(pin, HIGH);

  //delay(1000);
  //return;
  //Serial.print("sleep_enable\n");


  /* Now is the time to set the sleep mode. In the Atmega8 datasheet
     http://www.atmel.com/dyn/resources/prod_documents/doc2486.pdf on page 35
     there is a list of sleep modes which explains which clocks and
     wake up sources are available in which sleep modus.

     In the avr/sleep.h file, the call names of these sleep modus are to be found:

     The 5 different modes are:
         SLEEP_MODE_IDLE         -the least power savings
         SLEEP_MODE_ADC
         SLEEP_MODE_PWR_SAVE
         SLEEP_MODE_STANDBY
         SLEEP_MODE_PWR_DOWN     -the most power savings

     For now, we want as much power savings as possible,
     so we choose the according sleep modus: SLEEP_MODE_PWR_DOWN

  */
  set_sleep_mode(SLEEP_MODE_PWR_DOWN);   // sleep mode is set here

  sleep_enable();              // enables the sleep bit in the mcucr register
  // so sleep is possible. just a safety pin

  /* Now is time to enable a interrupt. we do it here so an
     accidentally pushed interrupt button doesn't interrupt
     our running program. if you want to be able to run
     interrupt code besides the sleep function, place it in
     setup() for example.

     In the function call attachInterrupt(A, B, C)
     A   can be either 0 or 1 for interrupts on pin 2 or 3.

     B   Name of a function you want to execute at interrupt for A.

     C   Trigger mode of the interrupt pin. can be:
                 LOW        a low level triggers
                 CHANGE     a change in level triggers
                 RISING     a rising edge of a level triggers
                 FALLING    a falling edge of a level triggers

     In all but the IDLE sleep modes only LOW can be used.
  */

  attachInterrupt(0, wakeUpNow, RISING ); // use interrupt 0 (pin 2) and run function
  // wakeUpNow when pin 2 gets LOW

  sleep_mode();                // here the device is actually put to sleep!!
  //

  sleep_disable();             // first thing after waking from sleep:
  // disable sleep...


  detachInterrupt(0);          // disables interrupt 0 on pin 2 so the
  // wakeUpNow code will not be executed
  // during normal running time.
  power_all_enable();/* Re-enable the peripherals. */

  delay(100);                 // wat 2 sec. so humans can notice the
  // interrupt.
  // LED to show the interrupt is handled
  digitalWrite (pin, LOW);      // turn off the interrupt LED

}

void wakeUpNow()
{ //Serial.print("wakeUpNow\n");
  f_sleepButton = 0;
  //digitalWrite(pin, LOW);
  //attachInterrupt(0,sleepNow, FALLING ); // 睡眠模式
}

void clearsleepTimer() {
  f_sleepTimer = 0;
}

 

Copyright 版权声明写法

正确的格式应该是:Copyright [dates] by [author/owner] 

© 通常可以代替Copyright, 但是不可以用(c)。 All Rights Reserved 在某些国家曾经是必须的,但是现在在大多数国家,都不是法律上必须有的字样。 

参见下面几个正确的格式: 

©1995-2004 Macromedia, Inc. All rights reserved. 

©2004 Microsoft Corporation. All rights reserved. 

Copyright © 2004 Adobe Systems Incorporated. All rights reserved. 

©1995-2004 Eric A. and Kathryn S. Meyer. All Rights Reserved. 

请注意标点符号和大小写的用法,这也是专业精神的一种体现。 

现在流行some rights reserved:creativecommons.org 

some rights reserved 和copyright 本身并不矛盾,但是其中的界限更多是一个道德问题,真正的保留一部分权力,是指给浏览者fair use 的权利,fair use的界定也决不是随便乱用,或者抄袭。 

甚至说,除了copyright, 还有copyleft,它的定义是为了程序员开发能够共享源代码的一个方式,英文里free, 并不仅仅是免费。 而且这种的源码公开免费使用,和版权也一点都不冲突。请大家不要误解。