SymPy vs. Sage

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SymPy vs. Sage

SymPy vs. Sage

SymPy and Sage are Computer algebra systems.

Computer Algebra System
A software program that facilitates symbolic mathematics. The core functionality of a CAS is manipulation of mathematical expressions in symbolic form.

SymPy

Sympy is a Python library for symbolic computation that aims to become a full-featured computer algebra system and to keep the code simple to promote extensibility and comprehensibility.

SymPy was started by Ondřej Čertík in 2005 and he wrote some code in 2006 as well. In 11 March 2007, SymPy was realeased to the public. The latest stable release of SymPy is 0.7.1 (29 July 2011). There are more than 120 contributors to SymPy.

SymPy can be used:

  • Inside Python, as a library
  • As an interactive command line, using IPython

SymPy is entirely written in Python and does not require any external libraries, but various programs that can extend its capabilites can be installed:

  • gmpy, Cython --> speed improvement
  • Pyglet, Matplotlib --> 2d and 3d plotting
  • IPython --> interactive sessions

SymPy is available online at SymPy Live. The site was developed specifically for SymPy. It is a simple web shell that looks similar to iSymPy under the standard Python interpreter. SymPy Live uses Google App Engine as computational backend.

+ +: small library, pure Python, very functional, extensible, large community.

- -: slow, needs better documentation.

Sage

Sage (previously SAGE) is a mathematical software with features covering many aspects of mathematics, including algebra, number theory and calculus.

Sage was created by William A. Stein and the development began in 2005. The first public release was in the same year (24 February 2005). The latest stable release of Sage is Sage 4.7.2 (23 May 2011). There are more than 150 contributors to Sage.

Sage can be used in several ways:

  • Notebook graphical interface
  • Interactive command line
  • Programs (writing interpreted programs)
  • Scripts (writing stand-alone Python scripts that use the Sage library)

The overall goal of Sage is to create a viable, free, open-source alternative to Maple, Mathematica, Magma and MATLAB. Sage integrates many specialized mathematics software into a common interface, for which a user needs to know only Python.

However, Sage is not pure Python, since it makes use of many external packages written in many other languages and it is actually a collection of dozens different computer algebra systems.

+ +: full scientific stack, very functional, fast, large community.

- -: very large, not a library, complicated design.

Sympy (!)= Sage

Both SymPy and Sage are cost free open source CASes written entirely in Python (although Sage contains Cython code as well), the first one being released under a modified BSD license and the latter under a GNU GPL license.

One of the differences between SymPy and Sage is the fact that Sage comes with a GUI - the Notebook graphical interface. This Notebook is useful because it allows you to write and run code, display 2d and 3d plots and organize and share your work. The Notebook is run by typing notebook() after you cd into the Sage directory and run ./sage. The notebook() command starts the Sage notebook and opens your default browser to view it. However, SymPy can use plotting as well, by installing Pyglet.

Operating System Support

System Windows Mac OS X Linux BSD Solaris Other
SymPy Yes Yes Yes Yes Yes Any system that supports Python
Sage No Yes Yes No Yes VMware image for MS-Windows users

Download & Installation

Sympy is distributed in various forms. It is possible to download source tarballs and packages from the Google Code page but it is also possible to clone the main Git repository or browse the code online. The only prerequisite is Python since Sympy is Python-based library. It is recommended to install IPython as well, for a better experience.

Sage can be installed either from a pre-built binary tarball or from source. The binary method is fastest and has fewest prerequisites. The source method may take a long time (from 1 hour to 14 days), depending on the computer (it took about two weeks to build Sage on the T-Mobile G1 Android telephone).

Functionality

System

Formula

editor

Arbitrary

precision

Calculus Solvers
Integration Integral transforms* Equations Inequalities Diophantine equations Differential equations
SymPy No Yes Yes No Yes Yes No Yes
Sage Yes Yes Yes Yes Yes Yes No Yes
System Solvers

Graph

theory

Number

theory

Quantifier

elimination

Boolean

algebra

Tensors
Recurrence relations
SymPy Yes No Yes No Yes Yes
Sage Yes Yes Yes Yes Yes Yes

* Will be available in SymPy 0.7.2

Some syntax differences

Sage and SymPy may look very similar, but those are two very different systems with completely different internal design, non-overlapping features sets (e.g. Sage is very good at number theory and abstract algebra, but SymPy has sophisticated pretty printing and code generation frameworks) and quite different semantics.

SymPy uses Python constructs only. Here is an example:

>>> 2/7        # Python evaluates this to 0
0

>>> from __future__ import division         # We obtain a different result if we import division from __future__
>>> 2/7
0.285714285714

In Sage, the example returns a Rational:

sage: 2/7
2/7

To obtain a Rational in SymPy, one of these methods must be used:

>>> from sympy import Rational
>>> Rational(2, 7)
2/7

>>> from sympy import S
>>> S(2)/7
2/7

In SymPy, to raise something to a power, you must use **, not ^ as the latter uses the Python meaning, which is xor.

However, in Sage, both ** and ^ can be used to perform exponentation. This shows that Sage has a modified version of Python.

In [1]: (x+1)^2
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
/home/aoi_hana/sympy/<ipython-input-6-52730bce1577> in <module>()
----> 1 (x+1)^2

TypeError: unsupported operand type(s) for ^: 'Add' and 'int'

In [2]: (x+1)**2
Out[2]:
       2
(x + 1)

sage: (x+1)^2
(x+1)^2

sage: (x+1)**2
(x+1)^2

Algebra

SymPy

To perform partial fraction decomposition apart(expr, x) must be used. To combine expressions, together(expr, x) is what you need. Here are some examples of these two and other common functions in iSymPy:

In [8]: 1/( (x**2+2*x+1)*(x**2-1) )
Out[8]:
           1
───────────────────────
⎛ 2    ⎞ ⎛ 2          ⎞
⎝x  - 1⎠⋅⎝x  + 2⋅x + 1⎠

In [9]: apart(1/( (x**2+2*x+1)*(x**2-1) ), x)
Out[9]:
      1           1            1            1
- ───────── - ────────── - ────────── + ─────────
  8⋅(x + 1)            2            3   8⋅(x - 1)
              4⋅(x + 1)    2⋅(x + 1)

In [10]: together(1/(x**2+2*x) - 3/(x+y) + 1/(x+y+z))
Out[10]:
x⋅(x + 2)⋅(x + y) - 3⋅x⋅(x + 2)⋅(x + y + z) + (x + y)⋅(x + y + z)
─────────────────────────────────────────────────────────────────
                  x⋅(x + 2)⋅(x + y)⋅(x + y + z)

The evalf() method and the N() function can be used to evaluate expressions:

In [20]: pi.evalf()
Out[20]: 3.14159265358979

In [23]: N(sqrt(2)*pi, 50)
Out[23]: 4.4428829381583662470158809900606936986146216893757

Integrals can be used like regular expressions and support arbitrary precision:

In [24]: Integral(x**(-2*x), (x, 0, oo)).evalf(20)
Out[24]: 2.0784499818221828310

Sage

Here are some examples of algebra in Sage:

sage: 1/( (x**2+2*x+1)*(x**2-1) )
1/((x^2 - 1)*(x^2 + 2*x + 1))

sage: expand((x-1)^2)
x^2 - 2*x + 1

sage: f = I + x - x
sage: simplify(f)
I

sage: f = (cos(x)*sin(y))/sin(y)+(sin(x)*cos(y))/sin(x)
sage: simplify(f)
cos(x) + cos(y)

In Sage, to return the exact value of expressions, n(), .n(digits) and numerical_approx(var, prec) are used:

sage: n(pi)
3.14159265358979

sage: N(sqrt(2)*pi, digits=50)
4.4428829381583662470158809900606936986146216893757

sage: numerical_approx(pi, prec=200)
3.1415926535897932384626433832795028841971693993751058209749

sage: f = x^(-2*x)
sage: f.integral(x, 1, +Infinity)
integrate(x^(-2*x), x, 1, +Infinity)
sage: show(integrate(x^(-2*x), x, 1, +Infinity))
int4.png

Calculus

Limits

SymPy

Limits in SymPy have the following syntax: limit(function, variable, point). Here are some examples:

Limit of f(x)= sin(x)/x as x -> 0

In [20]: from sympy import *

In [21]: x = Symbol('x')

In [22]: limit(sin(x)/x, x, 0)
Out[22]: 1

Limit of f(x)= 2*x+1 as x -> 5/2

In [24]: limit(2*x+1, x, S(5)/2)     # The *S()* method must be used for 5/2 to be Rational in SymPy
Out[24]: 6

Sage

The limit() function has this syntax: limit(ex, dir=None, taylor=False, algorithm=’maxima’, **argv):

sage: x = var('x')
sage: f = (1+1/x)^x
sage: f.limit(x = oo)
e

sage: f.limit(x = 5)
7776/3125

sage: f.limit(x = I, taylor=True)
(-I + 1)^I

sage: limit(2*x+1, x=5/2)       # 5/2 is Rational in Sage by default
6
Differentiation

SymPy

In [1]: from sympy import *

In [2]: x = Symbol('x')

In [3]: diff(cos(x**3), x)
Out[3]:
    2    ⎛ 3⎞
-3⋅x ⋅sin⎝x ⎠

In [4]: diff(atan(2*x), x)
Out[4]:
   2
────────
   2
4⋅x  + 1

In [6]: diff(1/tan(x), x)
Out[6]:
     2
- tan (x) - 1
─────────────
     2
  tan (x)

Sage

sage: var ('x')        # declaration of variable x
x
sage: f = cos(x**3); f
cos(x^3)
sage: f.diff(x)
-3*x^2*sin(x^3)
sage: show(f)          # show() is one of the pprint functions in Sage
so1.png
sage: show(f.diff(x))
so2.png
sage: f = atan(2*x); f
arctan(2*x)
sage: f.diff(x)
2/(4*x^2 + 1)
sage: show(f)
so3.png
sage: show(f.diff(x))
so4.png
sage: f = 1/tan(x); f
1/tan(x)
sage: f.diff(x)
-(tan(x)^2 + 1)/tan(x)^2
sage: show(f)
so5.png
sage: show(f.diff(x))
so6.png
Series expansion

SymPy

The syntax for series expansion is: .series(var, point, order):

In [27]: from sympy import *

In [28]: x = Symbol('x')

In [29]: cos(x).series(x, 0, 14)
Out[29]:
     2    4     6      8       10         12
    x    x     x      x       x          x         ⎛ 14⎞
1 - ── + ── - ─── + ───── - ─────── + ───────── + O⎝x  ⎠
    2    24   720   40320   3628800   479001600

In [30]: (1/cos(x**2)).series(x, 0, 14)
Out[30]:
     4      8       12
    x    5⋅x    61⋅x      ⎛ 14⎞
1 + ── + ──── + ────── + O⎝x  ⎠
    2     24     720

It is possible to make use of series(x*cos(x), x) by creating a wrapper around Basic.series().

In [31]: from sympy import Symbol, cos, series
In [32]: x = Symbol('x')
In [33]: series(cos(x), x)
Out[33]:
     2    4
    x    x     ⎛ 6⎞
1 - ── + ── + O⎝x ⎠
    2    24

Sage

Series expansion can be used with the taylor(f, *args) function:

sage: taylor(cos(x), x, 0, 14)
-1/87178291200*x^14 + 1/479001600*x^12 - 1/3628800*x^10 + 1/40320*x^8 - 1/720*x^6 + 1/24*x^4 - 1/2*x^2 + 1

sage: taylor(1/cos(x**2), x, 0, 14)
61/720*x^12 + 5/24*x^8 + 1/2*x^4 + 1

sage: var('x, k')
(x, k)
sage: taylor(sqrt (1 - k^2*sin(x)^2), x, 0, 6)
-1/720*(45*k^6 - 60*k^4 + 16*k^2)*x^6 - 1/24*(3*k^4 - 4*k^2)*x^4 - 1/2*k^2*x^2 + 1
Integration

SymPy

The integrals module in SymPy implements methods calculating definite and indefinite integrals of expressions. Principal method in this module is integrate():

  • integrate(f, x) returns the indefinite integral int1
  • integrate(f, (x, a, b)) returns the definite integral int2

SymPy can integrate:

  • polynomial functions:
In [6]: from sympy import *

In [7]: import sys

In [8]: from sympy import init_printing

In [9]: init_printing(use_unicode=False, wrap_line=False, no_global=True)

In [10]: x = Symbol('x')

In [11]: integrate(x**2 + 2*x + 4, x)
 3
x     2
── + x  + 4⋅x
3
  • rational functions:
In [1]: integrate((x+1)/(x**2+4*x+4), x)
Out[1]:
               1
log(x + 2) + ─────
             x + 2
  • exponential-polynomial functions:
In [5]: integrate(5*x**2 * exp(x) * sin(x), x)
Out[5]:
   2  x             2  x                             x             x
5⋅x ⋅ℯ ⋅sin(x)   5⋅x ⋅ℯ ⋅cos(x)        x          5⋅ℯ ⋅sin(x)   5⋅ℯ ⋅cos(x)
────────────── - ────────────── + 5⋅x⋅ℯ ⋅cos(x) - ─────────── - ──────────
      2                2                               2             2
  • non-elementary integrals:
In [11]: integrate(exp(-x**2)*erf(x), x)
  ___    2
╲╱ π ⋅erf (x)
─────────────
      4

Here is an example of a definite integral (Calculate integral1):

In [1]: integrate(x**2 * cos(x), (x, 0, pi/2))
Out[1]:
      2
     π
-2 + ──
     4

Sage

Sage can integrate some simple functions on its own:

  • polynomial functions:
sage: f = x^2 + 2*x + 4     # ** and ^ represent the same thing
sage: f.integral(x)
1/3*x^3 + x^2 + 4*x
  • rational functions:
sage: f = (x+1)/(x^2 + 4*x + 4)
sage: f.integral(x)
1/(x + 2) + log(x + 2)
  • exponential-polynomial functions:
sage: f = 5*x^2 * exp(x) * sin(x)
sage: f.integral(x)
5/2*(x^2 - 1)*e^x*sin(x) - 5/2*(x^2 - 2*x + 1)*e^x*cos(x)
  • non-elementary integrals:
sage: f = exp(-x**2)*erf(x)
sage: f.integral(x)
1/4*sqrt(pi)*erf(x)^2

The output of integral2 in Sage is:

sage: f = x^2 * cos(x)
sage: f.integral(x, 0, pi/2)
1/4*pi^2 - 2
Complex numbers

SymPy

In [1]: from sympy import Symbol, exp, I

In [2]: x = Symbol("x")

In [3]: exp(I*2*x).expand()
Out[3]:
 2⋅ⅈ⋅x
ℯ

In [4]: exp(I*2*x).expand(complex=True)
Out[4]:
   -2⋅im(x)                 -2⋅im(x)
ⅈ⋅ℯ        ⋅sin(2⋅re(x)) + ℯ        ⋅cos(2⋅re(x))

In [5]: x = Symbol("x", real=True)

In [6]: exp(I*2*x).expand(complex=True)
Out[6]: ⅈ⋅sin(2⋅x) + cos(2⋅x)

Sage

This is an example of a complex number in Sage:

sage: C = ComplexField()
sage: I = C.0
sage: b = 15/10 + 25/10*I
sage: b
1.50000000000000 + 2.50000000000000*I
Functions

SymPy

trigonometric

In [1]: cos(x-y).expand(trig=True)
Out[1]: sin(x)⋅sin(y) + cos(x)⋅cos(y)

In [2]: cos(2*x).expand(trig=True)
Out[2]:
     2
2⋅cos (x) - 1

In [3]: sinh(I*x**2)
Out[3]:
     ⎛ 2⎞
ⅈ⋅sin⎝x ⎠

In [11]: sinh(acosh(x))
Out[11]:
  _______   _______
╲╱ x - 1 ⋅╲╱ x + 1

zeta function

In [4]: zeta(5, x**2)
Out[4]:
 ⎛    2⎞
ζ⎝5, x ⎠

In [5]: zeta(5, 2)
Out[5]: ζ(5, 2)

In [6]: zeta(4, 1)
Out[6]:
 4
π
──
90

factorials and gamma function

In [7]: a = Symbol('a')

In [8]: b = Symbol('b', integer=True)

In [9]: factorial(a)
Out[9]: a!

In [13]: gamma(b+2).series(b, 0, 3)
Out[13]:
                        2  2             2  2
                       π ⋅b    EulerGamma ⋅b                2    ⎛ 3⎞
1 + b - EulerGamma⋅b + ───── + ────────────── - EulerGamma⋅b  + O⎝b ⎠
                         12          2

polynomials

In [14]: chebyshevt(8,x)
Out[14]:
     8        6        4       2
128⋅x  - 256⋅x  + 160⋅x  - 32⋅x  + 1

In [15]: legendre(3, x)
Out[15]:
   3
5⋅x    3⋅x
──── - ───
 2      2

In [16]: hermite(3, x**2)
Out[16]:
   6       2
8⋅x  - 12⋅x

Sage

trigonometric

sage: (cos(90)+sin(30)).n(100)
-1.4361052402220319423532262217

sage: (cos(3) + tan(3)).n(5)
-1.1

sage: sinh(arccosh(x), hold=True).simplify()
sqrt(x - 1)*sqrt(x + 1)

zeta function

The example below returns the Riemann zeta function evaluated at a complex number:

sage: i = ComplexField(30).gen()
sage: z = 1 + i
sage: z.zeta()
0.58215805981 - 0.92684856430*I
sage: zeta(z)
0.58215805981 - 0.92684856430*I

factorials and gamma function

The factorial(*args, coerce=True, hold=False, dont_call_method_on_arg=False) function return the factorial of n (the output is an integer or a symbolic expression).

sage: x = var('x')
sage: factorial(10)
3628800

The gamma() function is used for other nonnegative numbers that are not integers:

sage: x = var('x')
sage: factorial(3/4)
gamma(7/4)
sage: factorial(2.3)
2.68343738195577

These examples return the Gamma function and the incomplete form of it, evaluated for a complex number:

sage: i = ComplexField(30).0
sage: (1+i).gamma()
0.49801566824 - 0.15494982828*I

sage: C, i = ComplexField(30).objgen()
sage: (1+i).gamma_inc(2 + 3*i)
0.0020969148645 - 0.059981913655*I

polynomials

sage: x = polygen(QQ, 'x')
sage: chebyshev_U(2, x)
4*x^2 - 1

Special functions like chebyshev or bessel have only numerical use in Sage. For symbolic use, the Maxima interface included in Sage must be used directly:

sage: maxima.eval("f:bessel_y(v, w)")
'bessel_y(v,w)'
Differential equations

SymPy

In iSymPy:

In [10]: f(x).diff(x, x) + f(x)
Out[10]:
         2
        d
f(x) + ───(f(x))
         2
       dx

In [11]: dsolve(f(x).diff(x, x) + f(x), f(x))
Out[11]: f(x) = C₁⋅sin(x) + C₂⋅cos(x)

Sage

You can use Sage to investigate ordinary differential equations. To solve the equation x'+x-1=0:

sage: t = var('t')
sage: x = function('x', t)
sage: d = diff(x, t) + x - 1
sage: desolve(d, [x, t])
(c + e^t)*e^(-t)
Algebraic equations

SymPy

In iSymPy:

In [3]: solve(x**3 + 2*x**2 - 1, x)
Out[3]:
⎡            ___      ___    ⎤
⎢      1   ╲╱ 5     ╲╱ 5    1⎥
⎢-1, - ─ + ─────, - ───── - ─⎥
⎣      2     2        2     2⎦


In [5]: solve( [x**2 + 4*y**2 -2, -10*x + 2*y -15], [x, y])
Out[5]:
⎡⎛          ____              ____  ⎞  ⎛          ____              ____   ⎞⎤
⎢⎜  150   ╲╱ 23 ⋅ⅈ   15   5⋅╲╱ 23 ⋅ⅈ ⎟  ⎜  150   ╲╱ 23 ⋅ⅈ   15   5⋅╲╱ 23 ⋅  ⎟⎥
⎢⎜- ─── - ────────, ─── - ──────────⎟, ⎜- ─── + ────────, ─── + ────────── ⎟⎥
⎣⎝  101     101     202      101    ⎠  ⎝  101     101     202      101     ⎠⎦

Sage

The solve() function solves equations. To use it, you must specify some variables, then the argumens to solve are an equation (or a system of equations), together with the variables for which to solve. The function is the same as the solve() from SymPy:

sage: x = var('x')
sage: solve(x^3 + 2*x^3 - 1, x)
[x == 1/6*(I*sqrt(3) - 1)*3^(2/3), x == 1/6*(-I*sqrt(3) - 1)*3^(2/3), x == 1/3*3^(2/3)]

sage: x = var('x')
sage: solve( (x^2 + 4*y^2 -2, -10*x + 2*y -15), (x, y) )
[ [x == -1/101*I*sqrt(23) - 150/101, y == -5/101*I*sqrt(23) + 15/202], [x == 1/101*I*sqrt(23) - 150/101, y == 5/101*I*sqrt(23) + 15/202] ]

Linear Algebra

Matrices

SymPy

In SymPy, matrices are created as instances from the Matrix class:

In [1]: from sympy import Matrix

In [2]: Matrix([ [1, 0 , 0], [0, 1, 0], [0, 0, 1] ])
Out[2]:
⎡1  0  0⎤
⎢       ⎥
⎢0  1  0⎥
⎢       ⎥
⎣0  0  1⎦

It is possible to slice submatrices, since this is Python:

In [4]: M = Matrix(2, 3, [1, 2, 3, 4, 5, 6])

In [5]: M[0:2,0:2]
Out[5]:
⎡1  2⎤
⎢    ⎥
⎣4  5⎦

In [6]: M[1:2,2]
Out[6]: [6]

In [7]: M[:,2]
Out[7]:
⎡3⎤
⎢ ⎥
⎣6⎦

One basic operation involving matrices is the determinant:

In [8]: M = Matrix(( [2, 5, 6], [4, 7, 10], [1, 0, 3] ))

In [9]: M.det()
Out[9]: -10

print_nonzero(symb='x') shows location of non-zero entries for fast shape lookup.

In [10]: M = Matrix(( [2, 0, 0, 1, 0], [3, 5, 0, 1, 0], [10, 4, 0, 1, 2], [1, 6, 0, 0, 0], [0, 4, 0, 2, 2] ))
In [12]: M
Out[12]:
⎡2   0  0  1  0⎤
⎢              ⎥
⎢3   5  0  1  0⎥
⎢              ⎥
⎢10  4  0  1  2⎥
⎢              ⎥
⎢1   6  0  0  0⎥
⎢              ⎥
⎣0   4  0  2  2⎦

In [13]: M.print_nonzero()
[X  X ]
[XX X ]
[XX XX]
[XX   ]
[ X XX]

Matrix transposition with transpose():

In [14]: from sympy import Matrix, I

In [15]: m = Matrix(( (1,2+I), (3,4) ))

In [16]: m
Out[16]:
⎡1  2 + ⅈ⎤
⎢        ⎥
⎣3    4  ⎦

In [17]: m.transpose()
Out[17]:
⎡  1    3⎤
⎢        ⎥
⎣2 + ⅈ  4⎦

In [19]: m.T == m.transpose()
Out[19]: True

Sage

Sage provides standard constructions from linear algebra:

sage: A = Matrix([ [1, 0 , 0], [0, 1, 0], [0, 0, 1] ])
[1 0 0]
[0 1 0]
[0 0 1]

det(x) returns the determinant of x:

sage: M = MatrixSpace(QQ, 3, 3)
sage: A = M([2, 5, 6, 4, 7, 10, 1, 0, 3])
sage: det(A)
-10

It is not possible to define a matrix with various types of numbers.

sage: M = MatrixSpace(CC, 2, 2)   # Complex numbers matrix
sage: A = M( [1,2+I,3,4] )      # both integer and complex numbers
sage: transpose(A)
[1.00000000000000                           3.00000000000000]
[2.00000000000000 + 1.00000000000000*I      4.00000000000000]

sage: M = MatrixSpace(ZZ, 2, 2)   # integer numbers
sage: A = M( [1,2,3,4] )
sage: transpose(A)
[1 3]
[2 4]

Geometry

SymPy

The geometry module can be used to create two-dimensional geometrical entities and query information about them. These entities are available:

  • Point
  • Line, Ray, Segment
  • Ellipse, Circle
  • Polygon, RegularPolygon, Triangle

Check if points are collinear:

In [37]: from sympy import *

In [38]: from sympy.geometry import *

In [39]: x = Point(0, 0)

In [40]: y = Point(3, 1)

In [41]: z = Point(5, 5)

In [42]: Point.is_collinear(x, y, z)
Out[42]: False

In [43]: Point.is_collinear(x, z)
Out[43]: True

Segment declaration, slope, length, midpoint:

In [1]: import sympy

In [2]: from sympy import Point

In [3]: from sympy.abc import s

In [4]: from sympy.geometry import Segment

In [5]: Segment( (1, 2), (2, -3))
Out[5]: ((1,), (2,))

In [6]: s = Segment(Point(4, 3), Point(1, 1))

In [7]: s
Out[7]: ((1,), (4,))

In [8]: s.points
Out[8]: ((1,), (4,))

In [9]: s.slope
Out[9]: 2/3

In [10]: s.length
Out[10]:
  ____
╲╱ 13

In [11]: s.midpoint
Out[11]: (5/2,)

Sage

The point(points, **kwds) function return either a 2d or 3d point or sum of points. Here are some examples:

sage: point([(1,2), (1,3), (2,2)])
Points of a triangle
sage: point([(cos(theta), sin(theta)) for theta in srange(0, 2*pi, pi/8)]).show(frame=True)
The trigonometric circle highlighted by points

Pattern matching

SymPy

Using the .match method and the Wild class you can perform pattern matching on expressions. The method returns a dictionary with the needed substitutions. Here is an example:

In [11]: from sympy import *

In [12]: x = Symbol('x')

In [13]: y = Wild('y')

In [14]: (10*x**3).match(y*x**3)
Out[14]: {y: 10}

In [15]: s = Wild('s')

In [16]: (x**4).match(y*x**s)
Out[16]: {s: 4, y: 1}

SymPy returns None if the match is unsuccessful:

In [19]: print (x+1).match(y**x)
None

Sage

The wild(n=0) function returns the n-th wild-card for pattern matching and substitution:

sage: x,y = var('x,y')
sage: w0 = SR.wild(0); w1 = SR.wild(1)
sage: pattern = sin(x)*w0*w1^2; pattern
$0*$1^2*sin(x)
sage: f = atan(sin(x)*3*x^2); f
arctan(3*x^2*sin(x))
sage: f.has(pattern)
True
sage: f.subs(pattern == x^2)
arctan(x^2)

Printing

SymPy

There are many ways of printing mathematical expressions. Two of the most common methods are:

  • Standard printing
  • Pretty printing using the pprint() function
  • Pretty printing using the init_printing() method

Standard printing is the return value of str(expression):

>>> from sympy import Integral   # Python session
>>> from sympy.abc import c
>>> print c**3
c**3
>>> print 2/c
2/c
>>> print Integral(c**2+2*c, c)
Integral(c**2 + 2*c, c)

Pretty printing is a nice ascii-art printing with the help of a pprint function:

In [1]: from sympy import Integral, pprint   # IPython session (pprint enabled by default)

In [2]: from sympy.abc import c

In [3]: pprint(c**3)
 3
c

In [4]: pprint(2/c)
2
─
c

In [5]: pprint(Integral(c**2+2*c, c))
⌠
⎮ ⎛ 2      ⎞
⎮ ⎝c  + 2⋅c⎠ dc
⌡

However, the proper way to set up pretty printing in SymPy is to use init_printing(pretty_print=True, order=None, use_unicode=None, wrap_line=None, num_columns=None, no_global=False, ip=None):

>>> from sympy import init_printing
>>> init_printing(use_unicode=False, wrap_line=False, no_global=True)
>>> from sympy import Integral, Symbol
>>> x = Symbol('x')
>>> Integral(x**3+2*x+1, x)
  /
 |
 | / 3          \
 | \x  + 2*x + 1/ dx
 |
/
>>> init_printing(pretty_print=True)
>>> Integral(x**3+2*x+1, x)
⌠
⎮ ⎛ 3          ⎞
⎮ ⎝x  + 2⋅x + 1⎠ dx
⌡

Sage

There are three common ways to print expressions in Sage:

  • Standard printing
  • The show() function
  • Pretty printing

Standard printing in Sage is almost identical with the printing from SymPy (Note that there is no print() function in Sage):

sage: c = var('c')
c^3
sage: 2/c
2/c
sage: integrate(c**2+2*c, c)
1/3*c^3 + c^2

The show() function is the same as the pprint() function from SymPy:

sage: f = x^(-2*x)
sage: f.integral(x, 1, +Infinity)
integrate(x^(-2*x), x, 1, +Infinity)
sage: show(integrate(x^(-2*x), x, 1, +Infinity))
int4.png

The pretty_print() function can be considered similar to the show() function, but the output is slightly different (pretty_print() displays the integral on one line, whereas show() displays it on three lines.):

sage: pretty_print(integrate(x^(-2*x), x, 1, +Infinity))
int5.png

Plotting

SymPy

Pyglet is required to use the plotting function of SymPy in 2d and 3d. Here is an example:

>>> from sympy import symbols, Plot, cos, sin
>>> x, y = symbols('x y')
>>> Plot(sin(x*10)*cos(y*5) - x*y)
[0]: -x*y + sin(10*x)*cos(5*y), 'mode=cartesian'
Output of the plotting example

Sage

In Sage, you can produce filled-in shapes by creating a list of points (L in the example below) and then use the polygon command to plot the shape with boundary formed by those points. For example, here is a blue hypotrochoid. By typing show(p, axes=false), you can see this without any axes. Note that it is possible to add text to a plot.

sage: L = [[6*cos(pi*i/100)+5*cos((6/2)*pi*i/100), 6*sin(pi*i/100)-5*sin((6/2)*pi*i/100)] for i in range(200)]
sage: p = polygon(L, rgbcolor=(1/8,1/4,1/2))
sage: t = text("hypotrochoid", (5,4), rgbcolor=(1,0,0))
sage: show(p+t, axes=false)
Hypotrochoid (axes are disabled)

The function sin(x)/x has the following plot:

sage: plot(sin(x)/x, x, -100, 100).show(ymin=-1)
Output of sin(x)/x

Conclusion

SymPy and Sage are trying to become nice open source alternatives to Maple/Mathematica. Their goal is to be reasonably fast, easily extended with your own ideas, be callable from Python and could be used in real world problems. SymPy uses a different approach to achieve this goal, because it aims to be a lightweight normal Python module, whereas Sage aims to glue together every useful open source mathematics software package (that is why SymPy is included in Sage by default since version 2.7) and provide a transparent interface to all of them. Another advantage of SymPy is that since it is written in pure Python (and doesn't need anything else), it is perfectly multiplatform, it's small and easy to install and use.

You can choose to use either SymPy or Sage, depending on what your needs are. For more information you can go to the official sites of SymPy and Sage.