我正在尝试使用我sympy.Eq(func, var)在 lambda 中生成的方程。它似乎正在返回一个“添加”对象列表，我不确定如何使用。str我在使用之前尝试过对 a 进行类型转换eval，并且我尝试过from sympy import I，我认为这与问题有关。
这是代码和错误消息：
py solid.py -vy = (x-1.0) (x-3.0) *2 1.0 3.0 -axis y --方法盘
这是一个运行示例：
import sys
import argparse
import math
from scipy import integrate
from sympy import Symbol, Eq, solve, I
import numpy
import pylab
parser = argparse.ArgumentParser(description='Find the volume of the solid of rotation defined. Use * for multiplication and ** to raise a power. Bounds are set equal to the implicit variable. Trailing .0\'s must be used for constants, and parentheses must be escaped ( e.g. \(x-2\) ). Answers are accurate to 6 decimals')
parser.add_argument('var', choices='xy', help='x|y')
parser.add_argument('=', metavar='=', choices='=')
parser.add_argument('equation', help='continous function')
parser.add_argument('a', type=float, help='bound \'a\'')
parser.add_argument('b', type=float, help='bound \'b\'')
parser.add_argument('-axis', choices='xy', help='axis of revolution (default == x)')
parser.add_argument('-m', choices='ds', help='method (disk/shell)')
parser.add_argument('-g', action='store_true', help='show graph')
parser.add_argument('-v', action='store_true', help='verbose (for debugging)')
args = parser.parse_args()
y = Symbol('y')
x = Symbol('x')
def solve_for_implicit(func, var):
if var == 'x':
equation = Eq(eval(func), x)
func = solve(equation, y)
else:
equation = Eq(eval(func), y)
func = solve(equation, x)
return func
def volume(var, func, a, b, axis=None, method=None):
if axis == None: axis = 'x'
if method == 's': method = 'shell'
if method == 'd': method = 'disk'
if var == axis and axis == 'x':
if args.v: print 'x = y about x'
if not method == 'disk':
pass
else:
pass
elif var == axis and axis == 'y':
# SHELL METHOD
if args.v: print 'y = x about y'
if not method == 'disk':
# this is what should be used for y = x about y
if args.v: print 'using SHELL method'
func = eval('lambda x: ' + 'x*(' + func + ')')
integral = integrate.quad(func, a, b)
if args.v: print 'integral from', a, 'to', b, '=', integral[0]
answer = 2 * math.pi * integral[0]
if args.v: print '2*pi*', integral[0], '=', answer
else:
func = solve_for_implicit(func, var)
print func[0]
func = eval('lambda y: ' + '(' + str(func[0]) + ')**2')
integral = integrate.quad(func, a, b)
if args.v: print 'integral=', integral[0]
answer = math.pi * integral[0]
elif not var == axis and axis == 'y':
# DISK METHOD
if args.v: print 'x = y about y -- '
if not method == 'shell':
pass
else:
pass
elif not var == axis and axis == 'x':
# DISK
if args.v: print 'y = x about x --',
if not method == 'shell':
pass
else:
pass
return answer
print volume(args.var, args.equation, args.a, args.b, args.axis, args.m)
if args.g: graph(args.equation, args.a, args.b)
回溯（最后一次调用）：
文件“solid.py”，第 136 行，打印卷（args.var，args.equation，args.a，args.b，args.axis，args.m）文件“solid.py”。 py"，第 75 行，卷中 func = eval('lambda y: ' + '(' + func[0] + ')**2') TypeError: cannot concatenate 'str' and 'Add' objects
当我首先尝试将其类型转换为 str() 时，我得到了这个：
文件“solid.py”，第 136 行，打印卷（args.var，args.equation，args.a，args.b，args.axis，args.m）文件“solid.py”，第 76 行，卷积分 = 积分.quad(func, a, b) 文件“/usr/lib/python2.6/dist-packages/scipy/integrate/quadpack.py”，第 185 行，在 quad retval = _quad(func,a,b ,args,full_output,epsabs,epsrel,limit,points) 文件“/usr/lib/python2.6/dist-packages/scipy/integrate/quadpack.py”，第 249 行，在 _quad 返回 _quadpack._qagse(func,a ,b,args,full_output,epsabs,epsrel,limit) quadpack.error: 提供的函数没有返回有效的浮点数。
另外，print func[0]给出：
2.33333333333333 + (0.296296296296298 - y/2 + (-0.0877914951989024 + (0.592592592592595 - y) 2/4) (1/2)) (1/3)*(1/2 - I*3 (1/2)/2) + 0.444444444444444/((1/2 - I*3* (1/2)/2) (0.296296296296298 - y/2 + (-0.0877914951989024 + (0.592592592592595 - y) 2/4) (1/2))**( 1/3))
感谢大家的帮助，抱歉之前没有提供完整的脚本。