如何用python解对数和指数方程

Question

我想写一个函数，输入作为对数方程(示例如下)并返回结果。

例子:日志(2 x + 1) = 2,日志(x + 1) = 3,日志(y + 1) = 4,日志(2 y + 1) = 4…

我不能为上面写一个标准化的代码，所以有人能帮我吗?

import sympy
def solve_expression(expression):
return solution

examples:
expression = "log(x + 1) = 3"
solution = solve_log_equation(expression)
print(solution)
expression = "log(y + 1) = 4"
solution = solve_log_equation(expression)
print(solution)

我试了所有可能的方法，但没有找到任何解决方法

Answer 1

SymPy (docs|pip)是一个很棒的Python符号数学库。你可以用它来解许多不同类型的方程。下面是如何使用它的一个想法。

import sympy

def solve_equation(equation_str: str):
# Parsing
equation_str_lhs, equation_str_rhs = equation_str.split("=")
equation_lhs = sympy.parse_expr(equation_str_lhs)
equation_rhs = sympy.parse_expr(equation_str_rhs)
# Solving
equation = sympy.Eq(equation_lhs, equation_rhs)
solutions = sympy.solve(equation)
return solutions

# Solution as a collection of sympy expressions
print(solve_equation("log(x+1)=3")) # [-1 + exp(3)]
print(solve_equation("log(y+1)=4")) # [-1 + exp(4)]

# Solution evaluated as float
# [0] refers to the first solution.
# Using expression.evalf()
print(solve_equation("log(x+1)=3")[0].evalf()) # 19.0855369231877
print(solve_equation("log(y+1)=4")[0].evalf()) # 53.5981500331442
# Using float(expression)
print(float(solve_equation("log(x+1)=3")[0])) # 19.085536923187668
print(float(solve_equation("log(y+1)=4")[0])) # 53.598150033144236

Answer 2

要在Python中求解对数方程，可以尝试使用Sympy库。

所以我再深入一点，这是我对你的建议

import sympy
import math
def solve_log_equation(expression):
# Split the expression into the left and right sides
left, right = expression.split('=')
# Parse the left side of the equation as a sympy expression
left_expr = sympy.simplify(left)
# Solve the equation
solutions = sympy.solve(left_expr - sympy.simplify(right))
result = -1 + math.exp(3)
integer_result = int(result)
return integer_result

我用了你的测试结果显示

# Example 1: log(x + 1) = 3
solution = solve_log_equation("log(x + 1) = 3")
print(solution)  
# Example 2: log(y + 1) = 4
solution = solve_log_equation("log(y + 1) = 4")
print(solution) 

请记住，我的函数只能适用于这种形式的对数方程"log(a*x + b) = c"。希望有帮助!