day4 作业计算器
作业:计算器开发
(1)实现加减乘除及拓号优先级解析;
(2)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。
思路:
(1)首先我们要找到内存括号中的内容,使用正则表达式,在这里,内存括号中我们选取比较复杂的(-9-2*5/-3 + 7 /3*99/4*2998 +10 * 568/14 );
(2)找到内存括号中的内容之后,我们只要对内层括号中的内容就行计算,接下来只要重复找内存括号即可;
(3)首先把找到的内存字符串括号去掉-9-2*5/-3 + 7 /3*99/4*2998 +10 * 568/14;
(4)然后我们在进行修正,把字符串中的空格去掉,把“+-”转化为“-”,把“--”转化为“=”号;
(5)-9-2*5/-3+7/3*99/4*2998+10*568/14,这是上面整理得到的,下面,我们对它进行分割处理,以“+-”进行分割,并且提取字符串中所有的“+-”,放在两个列表中sign=["-","-","-","+","+"],formula_list = ["","9","2*5/","3","7/3*99/4*2998","10*568/14"];
(6)上面我们虽然得到了两个列表,但是我们发现,formula_list中包含"",这个会影响我们后续的运算,列表中还包含"2*5/",说明这个地方的列表后面跟着一个负数,我们必须进行处理,把这个接上,这样才能够正确的运算;
(7)处理"",得到sign=["-","-","+","+"],formula_list = ["-9","2*5/","3","7/3*99/4*2998","10*568/14"]
(8)处理"2*5/",这里要拼接后面的负数,得到sign=["-",,"+","+"],formula_list = ["-9","2*5/-3","7/3*99/4*2998","10*568/14"]
(9)下面,我们来执行乘除运算,把列表formula_list传递给处理乘除的函数,让里面的乘除进行运算,得到如下格式;
(10)formula_list = ["-9",-3.33334,173134.00001,405.71],然后把这个列表返回回去,执行加减运算;
(11)处理加减的函数接到参数,并且执行加减运算,得到结果res;
(12)用res替换正则匹配出来的字符串,如上面程序一直循环,即可得到结果;
插入一个别人写的代码,这是我见过写的最好的代码,思路环环相扣,很考验一个人的逻辑能力,思维能力,我看了几遍弄到了原理,并且坚持自己谢了一遍。如下:
import re def operator_update(formula): # 对formula公式进行 去除空字符,更新运算符处理 formula = formula.replace(" ", "") # 去除空字符 formula = formula.replace("+-", "-") formula = formula.replace("--", "+") return formula def calc_muldiv(formula_list): ''' 计算公式里面的乘除 :param formula: 列表 :return: ''' for index, element in enumerate(formula_list): if "*" in element or "/" in element: operators = re.findall("[*/]", element) calc_list = re.split("[*/]", element) num = None for i, e in enumerate(calc_list): if num: if operators[i - 1] == "*": num *= float(e) elif operators[i - 1] == "/": num /= float(e) else: num = float(e) formula_list[index] = num return formula_list def calc_plumin(operators, num_list): ''' 计算列表数字的加减 :param operators: 运算符列表 :param num_list: 进行运算的数字列表 :return: 返回计算结果 ''' num = None for i, e in enumerate(num_list): if num: if operators[i - 1] == "+": num += float(e) elif operators[i - 1] == "-": num -= float(e) else: num = float(e) return num def merge(plus_minus_operator, multiply_divide_list): ''' 把列表中这样的形式'2*' '-3*' '5/3*' '4/2'合并到一块 :param formula_list: :return: ''' for index, element in enumerate(multiply_divide_list): if element.endswith("*") or element.endswith("/"): multiply_divide_list[index] = element + plus_minus_operator[index] + multiply_divide_list[index + 1] del multiply_divide_list[index + 1] del plus_minus_operator[index] return merge(plus_minus_operator, multiply_divide_list) return plus_minus_operator, multiply_divide_list def bracket_calc(formula): ''' 对括号最内层的formula公式进行计算 :param formula: :return: ''' formula = re.sub("[()]", "", formula) # 去除两边的() formula = operator_update(formula) plus_minus_operator = re.findall("[+-]", formula) # 列表 '+' '-' 运算符 multiply_divide_list = re.split("[+-]", formula) # 列表 有'*' '/' if multiply_divide_list[0] == "": # multiply_divide_list列表第一个字符为空的话,表示一个数字为负号 multiply_divide_list[1] = "-" + multiply_divide_list[1] del plus_minus_operator[0] del multiply_divide_list[0] res = merge(plus_minus_operator, multiply_divide_list) plus_minus_operator = res[0] # 列表 '+' '-' 运算符 进行合并处理 multiply_divide_list = res[1] plus_minus_list = calc_muldiv(multiply_divide_list) # 生成只进行加减运算的列表 res = calc_plumin(plus_minus_operator, plus_minus_list) return res def calculate(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''' while True: formula_depth = re.search("\([^()]+\)", formula) if formula_depth: formula_depth = formula_depth.group() res = bracket_calc(formula_depth) formula = formula.replace(formula_depth, str(res)) print("\33[34;1m%s\33[0m" % (formula)) else: res = bracket_calc(formula) print("\33[31;1m结果:%s\33[0m" % (res)) exit() if __name__ == '__main__': formula = "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) )" calculate(formula)
我在上面的思路上自己谢了一遍,没有看代码,自己按照思路谢了一遍,这个还要继续研究,里面用到了很多方法。字符串的分裂,findall()等很多方法,还有当元素不存在的时候,如果先创建,还有-=,+=,*=,/=等方法,元素里面的值遍历之后相乘相除的情况:
import re #导入正则模块 formula = "1 - 2 * ( (60-30 +(-9-2*5/-3 + 7 /3*99/4*2998 +10 * 568/14 ) * (-40/5)) - (-4*3)/ (16-3*2) )" def formula_update(formula_deep): #对字符串formula_deep进行修整,去除空格,转换+-为-,转换--为+操作 formula_deep = formula_deep.replace(" ","") #去除空格 formula_deep = formula_deep.replace("+-","-") formula_deep = formula_deep.replace("--","+") return formula_deep def formula_correct(operator_signs,formula_list): if formula_list[0] == "": # 如果列表中第一个元素是"",说明元素前面是一个"-"号,此时,是没有必要分割的,因为是-9,分割会出现错误,所以先进行判断 formula_list[1] = "-" + formula_list[1] del operator_signs[0] del formula_list[0] print(operator_signs) print(formula_list) for i,e in enumerate(formula_list): if e.endswith("*") or e.endswith("/"): formula_list[i] = e + "-" + formula_list[i+1] del operator_signs[i] del formula_list[i+1] return operator_signs,formula_list def muldiv(formula_list): for index,element in enumerate(formula_list): if "*" in element or "/" in element: muldiv_signs = re.findall("[/*]",element) muldiv_lists = re.split("[/*]",element) num = None for i,e in enumerate(muldiv_lists): if num: if muldiv_signs[i-1] == "*": num *= float(e) elif muldiv_signs[i-1] == "/": num /= float(e) else: num = float(e) formula_list[index] = num return formula_list def add_min(operator_signs,formula_list): num = None for i,e in enumerate(formula_list): if num: if operator_signs[i-1] == "+": num += float(e) elif operator_signs[i-1] == "-": num -= float(e) else: num = float(e) return num def handle(formula_deep): formula_deep = re.sub("[()]", "", formula_deep) # 去除字符串的括号,然后进一步执行,去除空格,以及转换+-以及-- formula_deep = formula_update(formula_deep) # 对字符串进行修整,去除空格处理等 operator_signs = re.findall("[+-]", formula_deep) # 生成字符串中运算符的列表,因为要先执行乘法,要保留之前的运算符号,以便执行乘法后能够执行加减 formula_list = re.split("[+-]", formula_deep) # 生成列表,列表的作用是执行运算的元素,列表中有一些不合理的地方需要修正 ret = formula_correct(operator_signs, formula_list) # 对列表进行修正,修正列表开头元素是"",元素结尾是"/",或"*"的情况 operator_signs = ret[0] # 得到新的运算符号 formula_list = ret[1] # 得到新的运算列表 # 执行乘法运算 formula_list = muldiv(formula_list) # 得到不包含乘除的列表,下面只需要执行加减即可 res = add_min(operator_signs, formula_list) return res def main(formula): while True: formula_deep = re.search("\([^()]+\)",formula) #匹配内层括号,处理内存括号中的内容,来回循环,即可满足条件 if formula_deep: #匹配的内容不为空的时候执行程序,当匹配不到括号的时候,说明已经匹配结束了,里面不包含括号了 formula_deep = formula_deep.group() res = handle(formula_deep) formula = formula.replace(formula_deep,str(res)) else: res = handle(formula) print(res) exit() if __name__ == "__main__": formula = "1 - 2 * ( (60-30 +(-40/5) * (-9-2*5/-3 + 7 /3*99/4*2998 +10 * 568/14 )) - (-4*3)/ (16-3*2) )" main(formula)
运行结果如下:
[]
['-40/5']
['-', '-', '+', '+']
['-9', '2*5/', '3', '7/3*99/4*2998', '10*568/14']
['-', '-']
['60', '30', '8.0*173534.54761904766']
[]
['-4*3']
['-']
['16', '3*2']
['+']
['-1388246.3809523813', '12.0/10.0']
['-', '-']
['1', '2*', '1388245.1809523813']
result: 2776491.3619047627