benbenbang · December 7, 2019 19:54
diff --git a/sympy_get_coeff.py b/sympy_get_coeff.py
 # Example
 from sympy import *

 x, y = symbols('x y')
 f = x + 2*y + 1
 g = Rational(3,2)*pi + exp(I*x) / (x**2 + y)

 # coeff(x, n): As you can see, it is for finding the coefficient of "variables" in mathematical expressions.
 # So if you want to get the constant, `coeff` is not the method you're looking for

 # Method 1: A bit comlicated to use M. 1
 expr_f = Poly(f)  # Or you can do it explcitly expr = Poly(f, x, y)
 expr_g = Poly(g, exp(I*x), 1/(x**2 + y)) # Need to hard code the variable when the expression is getting more complex
 coeffs_f = expr_f.coeffs()
 coeffs_g = expr_g.coeffs()
 print(coeffs_f)  # [1, 2, 1]
 print(coeffs_g)  # [1, 3*pi/2]

 # Method 2: This one is preferable, since you don't need to hard code the Poly expression
 get_const = lambda expr: expr.func(*[var for var in expr.args if not var.free_symbols])
 const_f = get_const(f)
 const_g = get_const(g)
 print(const_f)  # 1
 print(const_g)  # 3*pi/2
	# Example
	from sympy import *

	x, y = symbols('x y')
	f = x + 2*y + 1
	g = Rational(3,2)pi + exp(Ix) / (x**2 + y)

	# coeff(x, n): As you can see, it is for finding the coefficient of "variables" in mathematical expressions.
	# So if you want to get the constant, `coeff` is not the method you're looking for

	# Method 1: A bit comlicated to use M. 1
	expr_f = Poly(f) # Or you can do it explcitly expr = Poly(f, x, y)
	expr_g = Poly(g, exp(Ix), 1/(x*2 + y)) # Need to hard code the variable when the expression is getting more complex
	coeffs_f = expr_f.coeffs()
	coeffs_g = expr_g.coeffs()
	print(coeffs_f) # [1, 2, 1]
	print(coeffs_g) # [1, 3*pi/2]

	# Method 2: This one is preferable, since you don't need to hard code the Poly expression
	get_const = lambda expr: expr.func(*[var for var in expr.args if not var.free_symbols])
	const_f = get_const(f)
	const_g = get_const(g)
	print(const_f) # 1
	print(const_g) # 3*pi/2