集合正则表达式，对计算表达式进行格式化处理，并计算最终结果：

import re def format_string(string): string = string.replace("--", "+") string = string.replace("-+", "-") string = string.replace("++", "+") string = string.replace("+-", "+") string = string.replace("*-", "*") string = string.replace("*+", "*") string = string.replace("/+", "/") string = string.replace(' ', '') return string def calc_mul_div(string): regular='\d+\.?\d*([*/]|\*\*)[\-]?\d+\.?\d*' while re.findall(regular, string): expression = re.search(regular, string).group() if expression.count("*")==1: x,y = expression.split("*") mul_result = str(float(x) * float(y)) string = string.replace(expression, mul_result) string = format_string(string) if expression.count("/"): x,y = expression.split("/") div_result = str(float(x) / float(y)) string = string.replace(expression, div_result) string = format_string(string) if expression.count('*')==2: x,y=expression.split('**') pow_result=1 for i in range(int(y)): pow_result*=int(x) string=string.replace(expression,str(pow_result)) string=format_string(string) return string def calc_add_sub(string): add_sub= regular='[\-]?\d+\.?\d*([+-][\-]?\d+\.?\d*' while re.findall(add_sub, string): add_sub_ex = re.search(add_sub, string).group() if add_sub_ex.count("+")==1: x,y = add_sub_ex.split("+") add_result = str(float(x) + float(y)) string = string.replace(add_sub_ex, add_result) string = format_string(string) if add_sub_ex.count("-"): sub_list = re.search(add_sub, string) for sub_str in sub_list: numbers = sub_str.split("-") if len(numbers) == 3: result = 0 for v in numbers: if v: result -= float(v) else: x,y = numbers result = float(x) - float(y) string = string.replace(sub_str, "+" + str(result)) string = format_string(string) return string def check_expression(string): check_result = True if not string.count("(") == string.count(")"): print("表达错误,括号示闭合！") check_result = False if re.findall('[a-z]+', string.lower()): print("表达式错误,包含非法字符！") check_result = False return check_result source='1 - 2 * ((60-30 +(-40/5) * (-9-2-5-4*5-6/3-40/8+5*9) - (-4*3)/ (16-3*2)))' if check_expression(source): print("source: ", source) print("eval result: ", eval(source)) source = format_string(source) print(source) while source.count("(") > 0: strs = re.search('\([^()]*\)', source).group() replace_str = calc_mul_div(strs) replace_str = calc_add_sub(replace_str) source = format_string(source.replace(strs,replace_str[1:-1])) else: replace_str = calc_mul_div(source) replace_str = calc_add_sub(replace_str) source = source.replace(source, replace_str) print("my result: ", source.replace("+",""))

执行结果：

source: 1 - 2 * ((60-30 +(-40/5) * (-9-2-5-4*5-6/3-40/8+5*9) - (-4*3)/ (16-3*2))) eval result: -29.4 1-2*((60-30+(-40/5)*(-9-2-5-4*5-6/3-40/8+5*9)-(-4*3)/(16-3*2)))