NumPy .edu
[Pages:17]NumPy
Computational Physics NumPy
Outline
Some Leftovers
Get people on line! Write a function / Write a script
NumPy
NumPy Arrays; Indexing; Iterating Creating Arrays Basic Operations Copying Linear Algebra
Calculate Something
Basic python doesn't know much ...
We must "import" useful functions from the "math" module:
> from math import sin imports the "sin" function
To call the sin function: sin(theta)
> from math import * imports all math functions
To call the sin function: sin(theta)
} > import math
imports the math module
To call the sin function: math.sin(theta)
My Advice: USE
> import math as m
imports math, calls it "m"
THESE
To call the sin function: m.sin(theta)
Write a function
In [10]: import math
In [11]: def sind(theta): ....: t = theta/180.*math.pi ....: return(math.sin(t)) ....:
In [12]: sind(90) Out[12]: 1.0
Return when done with defi nition
Write a script
Use Text Editor to create a fi le with python commands.
In this example: myscript.py
##if filele: :mmyyssccrirpipt.tp.pyy AA=='H'HeellloloWWoorlrdld!'!' pprirnint tAA
To run the script enter:
In [13]: run myscript.py Out[13]: Hello World!
Try some stuff out!
Defne some numbers and operate on them (+,-,*,/)
Build a long string by concatenating short strings
Select substrings in your long string using the : operator.
Write a "degree input" function to compute cosine.
Write a fle with all trig functions ready to accept degree arguments (e.g. sind, cosd, tand, atand, atan2d)
About NumPy
Python Lists
Lists can have any type of data
Locations of List items in memory is not predictable
This limits mathematical use of Lists as arrays.
NumPy Arrays
All data have same type
All data are together in memory
List Data NumPy Array Data
Learning about NumPy
See: wiki.Tentative_NumPy_Tutorial
NumPy creates a homogeneous, multidimensional, array.
Elements all have same type.
Each dimension of the array is called an axis.
Number of axes is called the "rank" of the array.
Positive numbers are used to index the data in the array, beginning with index 0, with one number for each axis of the array.
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