通过Python实现简单的计算器
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 re import functools def 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 ( "\033[33;1m减号[%s]处理结果:\033[0m" % formula, res ) return res def remove_duplicates(formula): formula = formula.replace( "++" , "+" ) formula = formula.replace( "+-" , "-" ) formula = formula.replace( "-+" , "-" ) formula = formula.replace( "--" , "+" ) formula = formula.replace( "- -" , "+" ) return formula def 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 ( "\033[31;1m[%s]运算结果=\033[0m" % formula, res ) return res def 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_dividend def 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 ( "\033[32;1m[%s]运算结果:\033[0m" % formula,total_res) return total_res def 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 ( '\033[41;1m----没拓号了...---\033[0m' ) print ( '\n\n\033[42;1m最终结果:\033[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) )" ) |