教学项目之-通过Python实现简单的计算器
计算器开发需求
- 实现加减乘除及拓号优先级解析
- 用户输入 1 - 2 * ( (60-30 +(-40/5) * (9-2*5/3 + 7 /3*99/4*2998 +10 * 568/14 )) - (-4*3)/ (16-3*2) )等类似公式后，必须自己解析里面的(),+,-,*,/符号和公式，运算后得出结果，结果必须与真实的计算器所得出的结果一致
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import reimport functoolsdef minus_operator_handler(formula): '''处理一些特殊的减号运算''' minus_operators = re.split("-",formula) calc_list= re.findall("[0-9]",formula) if minus_operators[0] == '': #第一值肯定是负号 calc_list[0] = '-%s' % calc_list[0] res = functools.reduce(lambda x,y:float(x) - float(y), calc_list) print(" 33[33;1m减号[%s]处理结果: 33[0m" % formula, res ) return resdef remove_duplicates(formula): formula = formula.replace("++","+") formula = formula.replace("+-","-") formula = formula.replace("-+","-") formula = formula.replace("--","+") formula = formula.replace("- -","+") return formuladef compute_mutiply_and_dividend(formula): '''算乘除,传进来的是字符串噢''' operators = re.findall("[*/]", formula ) calc_list = re.split("[*/]", formula ) res = None for index,i in enumerate(calc_list): if res: if operators[index-1] == "*": res *= float(i) elif operators[index-1] == "/": res /= float(i) else: res = float(i) print(" 33[31;1m[%s]运算结果= 33[0m" %formula, res ) return resdef handle_minus_in_list(operator_list,calc_list): '''有的时候把算术符和值分开后,会出现这种情况 ['-', '-', '-'] [' ', '14969037.996825399 ', ' ', '12.0/ 10.0 '] 这需要把第2个列表中的空格都变成负号并与其后面的值拼起来,恶心死了 ''' for index,i in enumerate(calc_list): if i == '': #它其实是代表负号,改成负号 calc_list[index+1] = i + calc_list[index+1].strip()def handle_special_occactions(plus_and_minus_operators,multiply_and_dividend): '''有时会出现这种情况 , ['-', '-'] ['1 ', ' 2 * ', '14969036.7968254'],2*...后面这段实际是 2*-14969036.7968254,需要特别处理下,太恶心了''' for index,i in enumerate(multiply_and_dividend): i = i.strip() if i.endswith("*") or i.endswith("/"): multiply_and_dividend[index] = multiply_and_dividend[index] + plus_and_minus_operators[index] + multiply_and_dividend[index+1] del multiply_and_dividend[index+1] del plus_and_minus_operators[index] return plus_and_minus_operators,multiply_and_dividenddef compute(formula): '''这里计算是的不带括号的公式''' formula = formula.strip("()") #去除外面包的拓号 formula = remove_duplicates(formula) #去除外重复的+-号 plus_and_minus_operators = re.findall("[+-]", formula) multiply_and_dividend = re.split("[+-]", formula) #取出乘除公式 if len(multiply_and_dividend[0].strip()) == 0:#代表这肯定是个减号 multiply_and_dividend[1] = plus_and_minus_operators[0] + multiply_and_dividend[1] del multiply_and_dividend[0] del plus_and_minus_operators[0] plus_and_minus_operators,multiply_and_dividend=handle_special_occactions(plus_and_minus_operators,multiply_and_dividend) for index,i in enumerate(multiply_and_dividend): if re.search("[*/]" ,i): sub_res = compute_mutiply_and_dividend(i) multiply_and_dividend[index] = sub_res #开始运算+,- print(multiply_and_dividend, plus_and_minus_operators) total_res = None for index,item in enumerate(multiply_and_dividend): if total_res: #代表不是第一次循环 if plus_and_minus_operators[index-1] == '+': total_res += float(item) elif plus_and_minus_operators[index-1] == '-': total_res -= float(item) else: total_res = float(item) print(" 33[32;1m[%s]运算结果: 33[0m" %formula,total_res) return total_resdef calc(formula): '''计算程序主入口, 主要逻辑是先计算拓号里的值,算出来后再算乘除,再算加减''' parenthesise_flag = True calc_res = None #初始化运算结果为None,还没开始运算呢,当然为None啦 while parenthesise_flag: m = re.search("([^()]*)", formula) #找到最里层的拓号 if m: #print("先算拓号里的值:",m.group()) sub_res = compute(m.group()) formula = formula.replace(m.group(),str(sub_res)) else: print(' 33[41;1m----没拓号了...--- 33[0m') print('
33[42;1m最终结果: 33[0m',compute(formula)) parenthesise_flag = False #代表公式里的拓号已经都被剥除啦if __name__ == '__main__': #res = calc("1 - 2 * ( (60-30 +(-40/5) * (9-2*5/3 + 7 /3*99/4*2998 +10 * 568/14 )) - (-4*3)/ (16-3*2) )") res = calc("1 - 2 * ( (60-30 +(-9-2-5-2*3-5/3-40*4/2-3/5+6*3) * (-9-2-5-2*5/3 + 7 /3*99/4*2998 +10 * 568/14 )) - (-4*3)/ (16-3*2) )") |
