Getting started with sympy

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Remarks

This section provides an overview of what sympy is, and why a developer might want to use it.

It should also mention any large subjects within sympy, and link out to the related topics. Since the Documentation for sympy is new, you may need to create initial versions of those related topics.

Alternate installation (not conda)

Alternate ways to install SymPy from conda. conda is the recommended way, but these are some alternate ways. Including: git, pip, etc.

'Hello World'

Sympy is a Python library for doing symbolic — rather than numeric — calculations.

For instance, consider the quadratic equation in x,

x**2 + HELLO * x + WORLD = 0

where HELLO and WORLD are constants. What's the solution of this equation?

In Python, using Sympy we can code,

from sympy import symbols, solve, latex

x, HELLO, WORLD = symbols('x, HELLO, WORLD')
print ( latex ( solve ( x**2 + HELLO * x + WORLD, x ) ) )
 

Since I made a call to Latex the solutions are almost ready for publication! Sympy provides the two of them packed in a list. Here's one:

one solution

If you need to do more work on an expression then you would leave out the call to latex.

Installing SymPy

The easiest and recommended way to install SymPy is to install Anaconda.

If you already have Anaconda or Miniconda installed, you can install the latest version with conda:

conda install sympy
 

Another way of installing SymPy is using pip:

pip install sympy
 

Note that this might require root privileges, so one might acually need

sudo pip install sympy
 

Most linux distributions also offer SymPy in their package repositories. For Fedora one would install SymPy with

sudo dnf install python-sympy
sudo dnf install python3-sympy
 

The first one installs the python 2 version of the package, the latter python 3.

On OpenSuse the respective commands are:

sudo zypper install python-sympy
sudo zypper install python3-sympy
 

The packages for OpenSuse 42.2 seem rather outdated, so one of the first methods should be prefered.

Integration and Differentiation

Sympy is made for symbolic math, so let's have a look at some basic integration and differentiation.

from sympy import symbols, sqrt, exp, diff, integrate, pprint                                                                                                                      

x, y = symbols('x y', real=True)                                                                                                                                                              

pprint(diff(4*x**3+exp(3*x**2*y)+y**2,x))                                                                                                                                          
pprint(diff(4*x**3+exp(3*x**2*y)+y**2,y))                                                                                                                                          
pprint(integrate(exp(x*y**2)+sqrt(x)*y**2,x))                                                                                                                                      
pprint(integrate(exp(x*y**2)+sqrt(x)*y**2,y))
 

First we import the necessary functions from sympy. Next we define our variables x and y. Note that these are considered complex by default, so we tell sympy that we want a simple example by making them real. Next we differentiate some expression with respect to x and then y. Finally we integrate some expression, again with respect to x and then y. The call of pprint ensures that our functions get written in some nice human readable style.

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Thursday, June 8, 2017
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