計算器開發

1. 實現加減乘除及拓號優先級解析
2. 用戶輸入 1 - 2 * ( (60-30 +(-40/5) * (9-2*5/3 + 7 /3*99/4*2998 +10 * 568/14 )) - (-4*3)/ (16-3*2) )等類似公式後，必須自己解析裏面的(),+,-,*,/符號和公式，運算後得出結果，結果必須與真實的計算器所得出的結果一致

  1 import re
  2 #檢查表達式合法性
  3 def check_expression(string):
  4     check_result = True
  5     #括號是否匹配
  6     if not string.count("
 
(") == string.count(")"):
  7         print("表達式錯誤，括號未閉合！")
  8         check_result = False
  9     if re.findall(‘[a-z]‘,string.lower()):
 10         print("表達式錯誤，包含非法字符！")
 11         check_result = False
 12 
 13     return check_result
 14 
 15 #格式化字符串
 16 def format_string(string):
 17     string = string.replace("
 
--","+")
 18     string = string.replace("-+","-")
 19     string = string.replace("++","+")
 20     string = string.replace("+-","-")
 21     string = string.replace("*+","*")
 22     string = string.replace("/+","/")
 23     string = string.replace(‘ ‘,‘‘)
 24     return string
 25 
 26 #計算乘，除法#(30+6*2)
 

 27 def calc_mul_div(string):
 28     #從字符串中獲取一個乘法的表達式
 29     # regular = "\d+\.{0,}\d{0,}[\*\/][\-]{0,}\d+\.{0,}\d{0,}"
 30     regular = "\d+\.?\d*([*/]|\*\*)[\-]?\d+\.?\d*"
 31     #如果還能找到乘或除法表達式
 32     while re.findall(regular,string):
 33         #獲取表達式
 34         expression = re.search(regular,string).group()
 35 
 36         #如果是乘法
 37         if expression.count("*")==1:
 38             #獲取要計算的兩個數
 39             x,y = expression.split("*")
 40             #計算結果
 41             mul_result = str(float(x) * float(y))
 42             #將計算的表達式替換為計算結果值
 43             string = string.replace(expression,mul_result)
 44             #格式化一下
 45             string = format_string(string)
 46 
 47         #如果是除法
 48         if expression.count("/"):
 49             #獲取要計算的兩個數
 50             x,y = expression.split("/")
 51             #計算除法
 52             div_result = str(float(x) / float(y))
 53             #用結果替換表達式
 54             string = string.replace(expression,div_result)
 55             string = format_string(string)
 56 
 57         if expression.count(‘*‘)==2:
 58             x,y = expression.split(‘**‘)
 59             pow_result = 1
 60             for i in range(int(y)):
 61                 pow_result*=int(x)
 62             string = string.replace(expression,str(pow_result))
 63             string = format_string(string)
 64     return string
 65 
 66 #計算加，減法
 67 def calc_add_sub(string):##(30+12-23+24-3)
 68     #(30+12-23+24-3)
 69     #定義正則表達式
 70     #add_regular = "[\-]{0,}\d+\.{0,}\d{0,}\+[\-]{0,}\d+\.{0,}\d{0,}"
 71     #sub_regular = "[\-]{0,}\d+\.{0,}\d{0,}\-[\-]{0,}\d+\.{0,}\d{0,}"
 72     add_regular = ‘[\-]?\d+\.?\d*\+[\-]?\d+\.?\d*‘
 73     sub_regular = ‘[\-]?\d+\.?\d*\-[\-]?\d+\.?\d*‘
 74 
 75     #開始加法
 76     while re.findall(add_regular,string):
 77         #把所有的加法都算完，獲取所有加法表達式
 78         add_list = re.findall(add_regular,string)
 79         for add_str in add_list:
 80             #獲取兩個加法的數
 81             x,y = add_str.split("+")
 82             add_result = "+" + str(float(x) + float(y))
 83             string = string.replace(add_str,add_result)
 84         string = format_string(string)
 85 
 86     #開始減法
 87     while re.findall(sub_regular,string):
 88         sub_list = re.findall(sub_regular,string)
 89         for sub_str in sub_list:
 90             numbers = sub_str.split("-")
 91             #-3-5的情況split會返回3個值
 92             if len(numbers) == 3:
 93                 result = 0
 94                 for v in numbers:
 95                     if v:
 96                         result -= float(v)
 97             else:
 98                 x,y = numbers
 99                 result = float(x) - float(y)
100             #替換字符串
101             string = string.replace(sub_str,"+" + str(result))
102         string = format_string(string)
103     return string
104 
105 
106 
107 
108 if __name__ == "__main__":
109     source = ‘1 - 2 * ( (60-30 +(-40/5) * (9-2*5/3 + 7 /3*99/4*2998 +10 * 568/14 )) - (-4*3)/ (16-3*2) )‘
110     #source = "2-((-40/5)*(4-3))"
111     #source = "3**2"
112     #source = "3*6*8"
113 
114     if check_expression(source):
115         print("source:",source)
116         print("eval result",eval(source))
117         source = format_string(source)
118         print(source)
119 
120         while source.count("(") > 0:
121             #格式化
122             #去括號，得到括號的字符串，結果如：(30+6/3)
123             strs = re.search(‘\([^()]*\)‘,source).group()
124             #將括號的表達式進行乘，除運算
125             replace_str = calc_mul_div(strs)
126             #將運算的結果在進行加，減運算
127             replace_str = calc_add_sub(replace_str)
128             #將括號的字符串替換為計算結果，結果包含()，替換時去掉():[1:-1]
129             source = format_string(source.replace(strs,replace_str[1:-1]))
130 
131         else:
132             #沒有括號就到最後單一表達式了
133             # 算乘除
134             replace_str = calc_mul_div(source)
135             #算加減
136             replace_str = calc_add_sub(replace_str)
137             source = source.replace(source,replace_str)
138         print("my result:",source.replace("+",""))

1 source: 1 - 2 * ( (60-30 +(-40/5) * (9-2*5/3 + 7 /3*99/4*2998 +10 * 568/14 )) - (-4*3)/ (16-3*2) )
2 eval result 2776672.6952380957
3 1-2*((60-30+(-40/5)*(9-2*5/3+7/3*99/4*2998+10*568/14))-(-4*3)/(16-3*2))
4 my result: 2776672.6952380957
5 
6 Process finished with exit code 0

Python 計算器開發