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sympy

🎯Skill

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What it does

Symbolically solves mathematical problems using Python, performing exact symbolic computations across algebra, calculus, physics, and code generation.

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sympy

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AddedFeb 4, 2026

Skill Details

SKILL.md

Use this skill when working with symbolic mathematics in Python. This skill should be used for symbolic computation tasks including solving equations algebraically, performing calculus operations (derivatives, integrals, limits), manipulating algebraic expressions, working with matrices symbolically, physics calculations, number theory problems, geometry computations, and generating executable code from mathematical expressions. Apply this skill when the user needs exact symbolic results rather than numerical approximations, or when working with mathematical formulas that contain variables and parameters.

Overview

# SymPy - Symbolic Mathematics in Python

Overview

SymPy is a Python library for symbolic mathematics that enables exact computation using mathematical symbols rather than numerical approximations. This skill provides comprehensive guidance for performing symbolic algebra, calculus, linear algebra, equation solving, physics calculations, and code generation using SymPy.

When to Use This Skill

Use this skill when:

  • Solving equations symbolically (algebraic, differential, systems of equations)
  • Performing calculus operations (derivatives, integrals, limits, series)
  • Manipulating and simplifying algebraic expressions
  • Working with matrices and linear algebra symbolically
  • Doing physics calculations (mechanics, quantum mechanics, vector analysis)
  • Number theory computations (primes, factorization, modular arithmetic)
  • Geometric calculations (2D/3D geometry, analytic geometry)
  • Converting mathematical expressions to executable code (Python, C, Fortran)
  • Generating LaTeX or other formatted mathematical output
  • Needing exact mathematical results (e.g., sqrt(2) not 1.414...)

Core Capabilities

1. Symbolic Computation Basics

Creating symbols and expressions:

```python

from sympy import symbols, Symbol

x, y, z = symbols('x y z')

expr = x*2 + 2x + 1

# With assumptions

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

n = symbols('n', integer=True)

```

Simplification and manipulation:

```python

from sympy import simplify, expand, factor, cancel

simplify(sin(x)2 + cos(x)2) # Returns 1

expand((x + 1)3) # x3 + 3x2 + 3x + 1

factor(x*2 - 1) # (x - 1)(x + 1)

```

For detailed basics: See references/core-capabilities.md

2. Calculus

Derivatives:

```python

from sympy import diff

diff(x*2, x) # 2x

diff(x*4, x, 3) # 24x (third derivative)

diff(x*2y*3, x, y) # 6xy*2 (partial derivatives)

```

Integrals:

```python

from sympy import integrate, oo

integrate(x2, x) # x3/3 (indefinite)

integrate(x**2, (x, 0, 1)) # 1/3 (definite)

integrate(exp(-x), (x, 0, oo)) # 1 (improper)

```

Limits and Series:

```python

from sympy import limit, series

limit(sin(x)/x, x, 0) # 1

series(exp(x), x, 0, 6) # 1 + x + x2/2 + x3/6 + x4/24 + x5/120 + O(x**6)

```

For detailed calculus operations: See references/core-capabilities.md

3. Equation Solving

Algebraic equations:

```python

from sympy import solveset, solve, Eq

solveset(x**2 - 4, x) # {-2, 2}

solve(Eq(x**2, 4), x) # [-2, 2]

```

Systems of equations:

```python

from sympy import linsolve, nonlinsolve

linsolve([x + y - 2, x - y], x, y) # {(1, 1)} (linear)

nonlinsolve([x2 + y - 2, x + y2 - 3], x, y) # (nonlinear)

```

Differential equations:

```python

from sympy import Function, dsolve, Derivative

f = symbols('f', cls=Function)

dsolve(Derivative(f(x), x) - f(x), f(x)) # Eq(f(x), C1*exp(x))

```

For detailed solving methods: See references/core-capabilities.md

4. Matrices and Linear Algebra

Matrix creation and operations:

```python

from sympy import Matrix, eye, zeros

M = Matrix([[1, 2], [3, 4]])

M_inv = M**-1 # Inverse

M.det() # Determinant

M.T # Transpose

```

Eigenvalues and eigenvectors:

```python

eigenvals = M.eigenvals() # {eigenvalue: multiplicity}

eigenvects = M.eigenvects() # [(eigenval, mult, [eigenvectors])]

P, D = M.diagonalize() # M = PDP^-1

```

Solving linear systems:

```python

A = Matrix([[1, 2], [3, 4]])

b = Matrix([5, 6])

x = A.solve(b) # Solve Ax = b

```

For comprehensive linear algebra: See references/matrices-linear-algebra.md

5. Physics and Mechanics

Classical mechanics:

```python

from sympy.physics.mechanics import dynamicsymbols, LagrangesMethod

from sympy import symbols

# Define system

q = dynamicsymbols('q')

m, g, l = symbols('m g l')

# Lagrangian (T - V)

L = m(lq.diff())*2/2 - mgl(1 - cos(q))

# Apply Lagrange's method

LM = LagrangesMethod(L, [q])

```

Vector analysis:

```python

from sympy.physics.vector import ReferenceFrame, dot, cross

N = ReferenceFrame('N')

v1 = 3N.x + 4N.y

v2 = 1N.x + 2N.z

dot(v1, v2) # Dot product

cross(v1, v2) # Cross product

```

Quantum mechanics:

```python

from sympy.physics.quantum import Ket, Bra, Commutator

psi = Ket('psi')

A = Operator('A')

comm = Commutator(A, B).doit()

```

For detailed physics capabilities: See references/physics-mechanics.md

6. Advanced Mathematics

The skill includes comprehensive support for:

  • Geometry: 2D/3D analytic geometry, points, lines, circles, polygons, transformations
  • Number Theory: Primes, factorization, GCD/LCM, modular arithmetic, Diophantine equations
  • Combinatorics: Permutations, combinations, partitions, group theory
  • Logic and Sets: Boolean logic, set theory, finite and infinite sets
  • Statistics: Probability distributions, random variables, expectation, variance
  • Special Functions: Gamma, Bessel, orthogonal polynomials, hypergeometric functions
  • Polynomials: Polynomial algebra, roots, factorization, Groebner bases

For detailed advanced topics: See references/advanced-topics.md

7. Code Generation and Output

Convert to executable functions:

```python

from sympy import lambdify

import numpy as np

expr = x*2 + 2x + 1

f = lambdify(x, expr, 'numpy') # Create NumPy function

x_vals = np.linspace(0, 10, 100)

y_vals = f(x_vals) # Fast numerical evaluation

```

Generate C/Fortran code:

```python

from sympy.utilities.codegen import codegen

[(c_name, c_code), (h_name, h_header)] = codegen(

('my_func', expr), 'C'

)

```

LaTeX output:

```python

from sympy import latex

latex_str = latex(expr) # Convert to LaTeX for documents

```

For comprehensive code generation: See references/code-generation-printing.md

Working with SymPy: Best Practices

1. Always Define Symbols First

```python

from sympy import symbols

x, y, z = symbols('x y z')

# Now x, y, z can be used in expressions

```

2. Use Assumptions for Better Simplification

```python

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

sqrt(x**2) # Returns x (not Abs(x)) due to positive assumption

```

Common assumptions: real, positive, negative, integer, rational, complex, even, odd

3. Use Exact Arithmetic

```python

from sympy import Rational, S

# Correct (exact):

expr = Rational(1, 2) * x

expr = S(1)/2 * x

# Incorrect (floating-point):

expr = 0.5 * x # Creates approximate value

```

4. Numerical Evaluation When Needed

```python

from sympy import pi, sqrt

result = sqrt(8) + pi

result.evalf() # 5.96371554103586

result.evalf(50) # 50 digits of precision

```

5. Convert to NumPy for Performance

```python

# Slow for many evaluations:

for x_val in range(1000):

result = expr.subs(x, x_val).evalf()

# Fast:

f = lambdify(x, expr, 'numpy')

results = f(np.arange(1000))

```

6. Use Appropriate Solvers

  • solveset: Algebraic equations (primary)
  • linsolve: Linear systems
  • nonlinsolve: Nonlinear systems
  • dsolve: Differential equations
  • solve: General purpose (legacy, but flexible)

Reference Files Structure

This skill uses modular reference files for different capabilities:

  1. core-capabilities.md: Symbols, algebra, calculus, simplification, equation solving

- Load when: Basic symbolic computation, calculus, or solving equations

  1. matrices-linear-algebra.md: Matrix operations, eigenvalues, linear systems

- Load when: Working with matrices or linear algebra problems

  1. physics-mechanics.md: Classical mechanics, quantum mechanics, vectors, units

- Load when: Physics calculations or mechanics problems

  1. advanced-topics.md: Geometry, number theory, combinatorics, logic, statistics

- Load when: Advanced mathematical topics beyond basic algebra and calculus

  1. code-generation-printing.md: Lambdify, codegen, LaTeX output, printing

- Load when: Converting expressions to code or generating formatted output

Common Use Case Patterns

Pattern 1: Solve and Verify

```python

from sympy import symbols, solve, simplify

x = symbols('x')

# Solve equation

equation = x*2 - 5x + 6

solutions = solve(equation, x) # [2, 3]

# Verify solutions

for sol in solutions:

result = simplify(equation.subs(x, sol))

assert result == 0

```

Pattern 2: Symbolic to Numeric Pipeline

```python

# 1. Define symbolic problem

x, y = symbols('x y')

expr = sin(x) + cos(y)

# 2. Manipulate symbolically

simplified = simplify(expr)

derivative = diff(simplified, x)

# 3. Convert to numerical function

f = lambdify((x, y), derivative, 'numpy')

# 4. Evaluate numerically

results = f(x_data, y_data)

```

Pattern 3: Document Mathematical Results

```python

# Compute result symbolically

integral_expr = Integral(x**2, (x, 0, 1))

result = integral_expr.doit()

# Generate documentation

print(f"LaTeX: {latex(integral_expr)} = {latex(result)}")

print(f"Pretty: {pretty(integral_expr)} = {pretty(result)}")

print(f"Numerical: {result.evalf()}")

```

Integration with Scientific Workflows

With NumPy

```python

import numpy as np

from sympy import symbols, lambdify

x = symbols('x')

expr = x*2 + 2x + 1

f = lambdify(x, expr, 'numpy')

x_array = np.linspace(-5, 5, 100)

y_array = f(x_array)

```

With Matplotlib

```python

import matplotlib.pyplot as plt

import numpy as np

from sympy import symbols, lambdify, sin

x = symbols('x')

expr = sin(x) / x

f = lambdify(x, expr, 'numpy')

x_vals = np.linspace(-10, 10, 1000)

y_vals = f(x_vals)

plt.plot(x_vals, y_vals)

plt.show()

```

With SciPy

```python

from scipy.optimize import fsolve

from sympy import symbols, lambdify

# Define equation symbolically

x = symbols('x')

equation = x*3 - 2x - 5

# Convert to numerical function

f = lambdify(x, equation, 'numpy')

# Solve numerically with initial guess

solution = fsolve(f, 2)

```

Quick Reference: Most Common Functions

```python

# Symbols

from sympy import symbols, Symbol

x, y = symbols('x y')

# Basic operations

from sympy import simplify, expand, factor, collect, cancel

from sympy import sqrt, exp, log, sin, cos, tan, pi, E, I, oo

# Calculus

from sympy import diff, integrate, limit, series, Derivative, Integral

# Solving

from sympy import solve, solveset, linsolve, nonlinsolve, dsolve

# Matrices

from sympy import Matrix, eye, zeros, ones, diag

# Logic and sets

from sympy import And, Or, Not, Implies, FiniteSet, Interval, Union

# Output

from sympy import latex, pprint, lambdify, init_printing

# Utilities

from sympy import evalf, N, nsimplify

```

Getting Started Examples

Example 1: Solve Quadratic Equation

```python

from sympy import symbols, solve, sqrt

x = symbols('x')

solution = solve(x*2 - 5x + 6, x)

# [2, 3]

```

Example 2: Calculate Derivative

```python

from sympy import symbols, diff, sin

x = symbols('x')

f = sin(x**2)

df_dx = diff(f, x)

# 2xcos(x**2)

```

Example 3: Evaluate Integral

```python

from sympy import symbols, integrate, exp

x = symbols('x')

integral = integrate(x exp(-x*2), (x, 0, oo))

# 1/2

```

Example 4: Matrix Eigenvalues

```python

from sympy import Matrix

M = Matrix([[1, 2], [2, 1]])

eigenvals = M.eigenvals()

# {3: 1, -1: 1}

```

Example 5: Generate Python Function

```python

from sympy import symbols, lambdify

import numpy as np

x = symbols('x')

expr = x*2 + 2x + 1

f = lambdify(x, expr, 'numpy')

f(np.array([1, 2, 3]))

# array([ 4, 9, 16])

```

Troubleshooting Common Issues

  1. "NameError: name 'x' is not defined"

- Solution: Always define symbols using symbols() before use

  1. Unexpected numerical results

- Issue: Using floating-point numbers like 0.5 instead of Rational(1, 2)

- Solution: Use Rational() or S() for exact arithmetic

  1. Slow performance in loops

- Issue: Using subs() and evalf() repeatedly

- Solution: Use lambdify() to create a fast numerical function

  1. "Can't solve this equation"

- Try different solvers: solve, solveset, nsolve (numerical)

- Check if the equation is solvable algebraically

- Use numerical methods if no closed-form solution exists

  1. Simplification not working as expected

- Try different simplification functions: simplify, factor, expand, trigsimp

- Add assumptions to symbols (e.g., positive=True)

- Use simplify(expr, force=True) for aggressive simplification

Additional Resources

  • Official Documentation: https://docs.sympy.org/
  • Tutorial: https://docs.sympy.org/latest/tutorials/intro-tutorial/index.html
  • API Reference: https://docs.sympy.org/latest/reference/index.html
  • Examples: https://github.com/sympy/sympy/tree/master/examples