Python符号计算之实现函数极限的方法
SymPy是符号数学的Python库。它的目标是成为一个全功能的计算机代数系统，同时保持代码简洁、易于理解和扩展
#coding:utf-8
'''
函数极限
'''
import sympy
sympy.init_printing()
from sympy import I, pi, oo
import numpy as np
x = sympy.Symbol('x')
expr = sympy.sin(x) / x
result = sympy.limit(expr,x,0)
print('limit:',result)
f = sympy.Function('f')
x, h = sympy.symbols("x, h")
diff_limit = (f(x + h) - f(x))/h
result = sympy.limit(diff_limit.subs(f, sympy.cos), h, 0)
print('limit:',result)
result = sympy.limit(diff_limit.subs(f, sympy.sin), h, 0)
print('limit:',result)
expr = (x**2 - 3*x) / (2*x - 2)
p = sympy.limit(expr/x, x, sympy.oo)
q = sympy.limit(expr - p*x, x, sympy.oo)
print('result:p,q = ',p,q)
# 求和
n = sympy.symbols("n", integer=True)
s = sympy.Sum(1/(n**2), (n, 1, oo))
print('sum:',s)
print('sum:',s.doit())
# 求积
p = sympy.Product(n, (n, 1, 7))
print('product:',p)
print('product:',p.doit())
expr = sympy.Sum((x)**n/(sympy.factorial(n)), (n, 1, oo)).doit().simplify()
print('expr:',expr)
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