import re
def md(l,x): a = l.index(x) if x = = '*' and l[a + 1 ] ! = '-' : k = float (l[a - 1 ]) * float (l[a + 1 ]) elif x = = '/' and l[a + 1 ] ! = '-' : k = float (l[a - 1 ]) / float (l[a + 1 ]) elif x = = '*' and l[a + 1 ] = = '-' : k = - ( float (l[a - 1 ]) * float (l[a + 2 ])) elif x = = '/' and l[a + 1 ] = = '-' : k = - ( float (l[a - 1 ]) / float (l[a + 2 ])) del l[a - 1 ], l[a - 1 ], l[a - 1 ] l.insert(a - 1 , str (k)) return l def fun(s): l = re.findall( '([\d\.]+|/|-|\+|\*)' ,s) sum = 0 while 1 : if '*' in l and '/' not in l: md(l, '*' ) elif '*' not in l and '/' in l: md(l, '/' ) elif '*' in l and '/' in l: a = l.index( '*' ) b = l.index( '/' ) if a < b: md(l, '*' ) else : md(l, '/' ) else : if l[ 0 ] = = '-' : l[ 0 ] = l[ 0 ] + l[ 1 ] del l[ 1 ] sum + = float (l[ 0 ]) for i in range ( 1 , len (l), 2 ): if l[i] = = '+' and l[i + 1 ] ! = '-' : sum + = float (l[i + 1 ]) elif l[i] = = '+' and l[i + 1 ] = = '-' : sum - = float (l[i + 2 ]) elif l[i] = = '-' and l[i + 1 ] = = '-' : sum + = float (l[i + 2 ]) elif l[i] = = '-' and l[i + 1 ] ! = '-' : sum - = float (l[i + 1 ]) break return sum def calculate(expression): ex = [] ans = 0 if '(' not in expression: ans = fun(expression) return ans for i in range ( len (expression)): if expression[i] = = '(' : ex.append(i) #ex=[6,7] elif expression[i] = = ')' : #14 temp = 0 sub = expression[ex[ len (ex) - 1 ] + 1 :i] temp = fun(sub) expression = expression[ 0 :ex[ len (ex) - 1 ]] + str (temp) + expression[i + 1 : len (expression) + 1 ] ex.pop() return calculate(expression) s = '1 - 2 * ( (60-30 +(-40/5+3) * (9-2*5/3 + 7 /3*99/4*2998 +10 * 568/14 )) - (-4*3)/ (16-3*2) )' print ( 1 - 2 * ( ( 60 - 30 + ( - 40 / 5 + 3 ) * ( 9 - 2 * 5 / 3 + 7 / 3 * 99 / 4 * 2998 + 10 * 568 / 14 )) - ( - 4 * 3 ) / ( 16 - 3 * 2 ) )) #1735397.4095238098 s3 = '3*(4+50)-((100+40)*5/2-3*2*2/4+9)*(((3+4)-4)-4)' #518.0 print ( 3 * ( 4 + 50 ) - (( 100 + 40 ) * 5 / 2 - 3 * 2 * 2 / 4 + 9 ) * ((( 3 + 4 ) - 4 ) - 4 )) print (calculate(s)) #1735397.4095238098 print (calculate(s3))
1，在没有括号的情况下：
def multdiv(l,x): #定义最小的乘除运算单元，l是列表，x代表*或/
a = l.index(x) #首先获取乘除运算符的位置 if x = = '*' and l[a + 1 ] ! = '-' : #判断*，/后面的一个操作符是否是‘-’如果是的话，分别进行处理 k = float (l[a - 1 ]) * float (l[a + 1 ]) elif x = = '/' and l[a + 1 ] ! = '-' : k = float (l[a - 1 ]) / float (l[a + 1 ]) elif x = = '*' and l[a + 1 ] = = '-' : k = - ( float (l[a - 1 ]) * float (l[a + 2 ])) elif x = = '/' and l[a + 1 ] = = '-' : k = - ( float (l[a - 1 ]) / float (l[a + 2 ])) del l[a - 1 ], l[a - 1 ], l[a - 1 ] #删除掉列表里刚做运算的三个元素，比如，3 * 2 l.insert(a - 1 , str (k)) #将刚计算的结果插入到列表中然后执行下一次计算 return l def fun(l): sum = 0 print (l) while 1 : #先将乘除运算计算完，在计算加减 if '*' in l and '/' not in l: #先判断，如果只有*的话，先计算 * multdiv(l, '*' ) elif '*' not in l and '/' in l: #如果只有 /的话，先计算 / multdiv(l, '/' ) elif '*' in l and '/' in l: #如果既有 / 也有 *的话，先获取他们的下标， a = l.index( '*' ) #根据下标判断先执行哪个 b = l.index( '/' ) if a < b: multdiv(l, '*' ) else : multdiv(l, '/' ) else : #当上面的乘除计算完之后，就可以计算加减了 print (l) if l[ 0 ] = = '-' : #这里需要判断一下，如果列表里第一个符号是‘-’ l[ 0 ] = l[ 0 ] + l[ 1 ] #的话，表示第一个数是负数，所以我们需要将列表第一和第二项合并起来 del l[ 1 ] sum + = float (l[ 0 ]) #做完上面的处理后列表中就只剩加减计算了， for i in range ( 1 , len (l), 2 ): if l[i] = = '+' and l[i + 1 ] ! = '-' : #判断+，-后面的一个操作符是否是‘-’如果是的话，分别进行处理 sum + = float (l[i + 1 ]) elif l[i] = = '+' and l[i + 1 ] = = '-' : sum - = float (l[i + 2 ]) elif l[i] = = '-' and l[i + 1 ] = = '-' : sum + = float (l[i + 2 ]) elif l[i] = = '-' and l[i + 1 ] ! = '-' : sum - = float (l[i + 1 ]) break return sum #最后返回这个不含括号表达式的结果 2在有括号的情况下
def calculate(expression): ex = [] #存储'('出现的位置 ans = 0 #保存结果 if '(' not in expression: #如果括号都处理完成了，直接调用fun函数返回结果 ans = fun(expression) return ans for i in range ( len (expression)): if expression[i] = = '(' : ex.append(i) #ex=[6,7] #纪录 '(' 出现的位置 elif expression[i] = = ')' : #遇到 ')'后。就可以计算第一个括号里的值 temp = 0 #定义一个变量 存储括号表达式的结果 sub = expression[ex[ len (ex) - 1 ] + 1 :i] #获取括号里的表达式 temp = fun(sub) #调用fun函数计算括号里的表达式的值 expression = expression[ 0 :ex[ len (ex) - 1 ]] + str (temp) + expression[i + 1 : len (expression) + 1 ] #去掉刚才的括号表达式，并用temp代替，返回一个新的表达式 ex.pop() #删除刚才计算完的括号表达式里面 '(' 的位置 return calculate(expression) #递归计算新的表达式，直道所有的括号处理完毕