numpy 如何在Python中求解对数和指数方程

4dbbbstv 于 2023-04-06 发布在 Python

关注(0)|答案(3)|浏览(198)

我正在尝试写一个函数，它以对数方程为输入（示例如下）并返回结果。
例如：log（2x+1）=2，log（x+1）=3，log（y+1）=4，log（2y+1）=4……
我不能写一个标准化的代码，所以上面有人可以帮助我。

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)

我尝试了所有的可能性，但找不到任何解决办法

numpy

来源：https://stackoverflow.com/questions/75944582/how-to-solve-logarithm-and-exponential-equations-in-python

3条答案

按热度按时间

yshpjwxd1#

SymPy（docs|pip）是Python中一个很棒的符号数学库。你可以用它来解决许多不同类型的方程。这里是如何使用它的想法。

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

赞(0）回复(0）举报 2023-04-06

ig9co6j12#

要在Python中求解对数方程，您可以尝试Sympy库。
所以我想再深入一点，这是我给你们的建议

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

# 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，我的函数只能用于对数方程的形式“log（a*x + B）= c”。希望它有帮助！

赞(0）回复(0）举报 2023-04-06

fxnxkyjh3#

也许你应该把你的字符串分成两部分，让左边的部分更像Python，就像用math.log替换log，然后用一个二分法来计算它？

赞(0）回复(0）举报 2023-04-06