"Python编程教程：地理处理脚本与GIS建模，数据管理与决策"。

版权申诉

3 浏览量更新于2024-02-22 收藏 410KB PDF 举报

身份认证购VIP最低享 7 折!

领优惠券(最高得80元）

资源详情

资源推荐

math and random modules

Many common mathematical functions are accessed via the math module. For instance, you

would need this for trigonometric functions or logarithms. (To use complex numbers, use

cmath which has similar functions, but allows for complex number results.)

 As before, try the following statements in the interactive window. (Feel free to run some of

these in programs as well, just remember to include the import statement at the top.)

Enter: Results: Notes:

import math

print math.log10(100)

Enter it before you use it

All module functions are prefaced with

the module name. This allows for re-

use of function names in different

modules.

print math.log(100)

Natural log

print math.pi

pi is a constant, so it doesn't need

parentheses

pi = math.pi

print pi

If you don’t want to type “math.pi” all

the time, assign it to a variable pi.

You don’t have to say “print” to see the

value of a variable. Print formats it –

handy sometimes, but not for this.

print math.sin(radians)

print math.cos(radians)

print math.tan(radians)

Trig functions use radians (same as all

languages and Excel). Try 0.7854

radians (same as 45 degrees)

degrad = pi /180

45 * degrad

Convert degrees to radians

sin = math.sin

sin(45 * degrad)

sin(90 * degrad)

Even functions (like sin) can be

assigned to a variable. Try it with cos

and tan too.

math.e

math.hypot(3,4)

What's a hypotenuse?

x1 = 520382; y1 = 4152373

x2 = 520475; y2 = 4152963

You can put multiple statements on a

line with a semicolon.

xr = x2 – x1

yr = y2 – y1

math.hypot(xr, yr)

math.sqrt(xr**2+yr**2)

(xr*xr+yr*yr)**0.5

Pythagorus invented Python, right?

For this example, think UTM

coordinates. What do the results

represent?

import random

random.random()

rnd = random.random

rnd()

Enter the method or function multiple

times to get multiple results.

mu = 50

s = 10

print random.gauss(mu, s)

Enter the print statement multiple times

to get multiple results.

 Optional: Look up the math and random modules in the help system to see what else they can

do. For matrix operations, download numpy or other numeric modules.

1.6 Creating functions with def

Somewhat similar to a module, but much simpler, is a function you define in your code to be used

simply by using the function name later in your code, and providing any parameters you want to use.

The function can thus be used as a variable in your program. This is easier to understand with an

example. The following code defines a radians function that simply converts degrees to radians, and

also defines a degrees function that converts radians to degrees. There are similarly named built-in

functions in Excel.

 From here on out, we’ll want to write scripts and save them into your “mypy” folder. For each

script use Ctrl-n or File New to create a new script. Maximize your PythonWin screen so you can

see both the script and the interactive window (where outputs go). Then after composing it, save it

to your “mypy” folder, and run the script with

the run button. In some cases, I’ll suggest

names for your scripts; otherwise make one up.

 Try the following code in a script saved into

your d:/prog/py folder as defRadians.py.

import math

def radians(angdeg):

return angdeg * math.pi / 180

def degrees(angrad):

return angrad * 180 / math.pi

print math.sin(radians(45))

print degrees(math.acos(0.5))

 Note the use of the return keyword to specify what value to return to the function when you

use it. Thus the radians function returns the result of the expression angdeg * math.pi / 180

whenever the radians( ) function is evoked, with the value in parentheses being processed as

angdeg in the function definition. Note the colon and indentation.

 There are many other uses for function definitions, some you'll see in the later examples. In

this code, we provided constants (45 and 0.5), but can you see how you could use this kind of

capability in a program where your data might be read from files, etc.

 Trigonometric functions are commonly used when working with field survey measurements,

such as with a compass, and since compasses all read in degrees instead of radians the above

conversions are commonly needed.

? Challenge: How would you change the program code so that you could have the print

statements read:

print sin(radians(45))

print degrees(acos(0.5))

? Challenge: Though this would be unconventional, you could also set up your code to always

work in degrees. How would you write your code so that you could write the statements as:

print sin(45)

print acos(0.5)

Optional: try the same things with a scientific

calculator or use the built-in Windows

Calculator program (in Accessories) with the

View set to "Scientific" – you can set the

calculator to work in degrees or radians. On

the calculator, enter 45, make sure the Degrees

option is chosen, and press the sin button.

Write down the result to 5 or so decimal places.

Then enter 0.5 and press the Inv option and

then press the cos button. Compare its results to

the code here.

剩余44页未读，继续阅读

梅里雪山GIS

粉丝: 2w+
资源: 500

会员权益专享

"Python编程教程：地理处理脚本与GIS建模，数据管理与决策"。

geoprocessing scripts with python.pdf

Geoprocessing-with-Python.pdf.pdf

Geoprocessing with python 百度云下载链接.txt

geoprocessing with python

arcgis 10.8文献引用

arcgis的python如何升级

arcgis中如何打开并运行python

怎么查找ArcGIS Python环境位置

使用ArcGIS附带的Python解释器

arcgis怎么运行python

ArcGIS Desktop怎么配置arcpy环境？

python中如何导入arcpy模块

ArcGIS教程：地理处理服务示例

如何配置arcgis10.2的python开发环境

面向arcgis的python脚本编程

没有Python包管理器啊

ArcGIS API for JavaScript里的tasks模块的具体功能

arcgis如何批量给字段赋值

请告诉我arcgis的分区统计工具的C#函数

arcpy使用手册pdf

会员权益专享

最新资源