Simple calculator implemented by Python

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Actually, python is a very powerful calculator: ^ _ ^,

<喎?http: www.bkjia.com kf ware vc " target="_blank" class="keylink"> VcD4KPHA + kernel + PC9wPgo8cHJlIGNsYXNzPQ = "brush: java;" >__ author _ = 'job' class ExpStack (): # init method def _ init _ (self ): self. top =-1 self. data = [] # whether Stack is empty def is_empty (self): return-1 = self. top # pop an element from stack def pop (self): if self. is_empty (): print "Stack is Empty... "else: self. data. pop (self. top) self. top-= 1 # push an element into stack d Ef push (self, e): self. data. append (e) self. top + = 1 # get an element in the top of the stack def get_top (self): if self. is_empty (): print "Stack is Empty" return None else: return self. data [self. top] # get the size of the stack def size (self): return self. top + 1 # clear stack def clear (self): self. top =-1 self. data = [] # get data of stack def get_data (self): return self. data # whether a char is a num Berdef is_number (char ): return ("0" = char or "1" = char or "2" = char or "3" = char or "4" = char or "5" = char or "6" = char or "7" = char or "8" = char or "9" = char) # whether a char is dotdef is_dot (char): return ". "= char # whether a char is calculator operationdef is_calculator_option (char ): return ("+" = char or "-" = char or "*" = char or "/" = char or "(" = char or ") "= ch Ar or "^" = char) # get calculator stringdef get_calculator_str (): return raw_input ("Please input calculator string (no '=') end with '-1 ': \ n ") # whether a string consists of numbersdef is_number_str (m_str): for n in m_str: if (not is_number (n) and (not is_dot (n )): return False return True # filter blks from a stringdef str_trim (src_str): ret_str = "" for c in src_str: if ""! = C: ret_str + = c return ret_str # filter useless characters from a stringdef str_filter (src_str): ret_str = "" for c in src_str: if is_number (c) or is_calculator_option (c) or is_dot (c): ret_str + = c return ret_str # print elements in the stackdef print_calculator_stack (stack): print "--- stack content ---" print stack. get_data () print # compare operators, return an integer #1: higher priority; 0: lower prio Rity;-1: wrong operator; 2: same prioritydef compare_operator (op1, op2): if "^" = op1: if "^" = op2: return 2 elif "+" = op2 or "-" = op2 or "*" = op3 or "/" = op3: return 1 else: return-1 elif "*" = op1 or "/" = op1: if "^" = op2: return 0 elif "*" = op2 or "/" = op2: return 2 elif "+" = op2 or "-" = op2: return 1 else: return-1 elif "+" = op1 or "-" = op1: if "^" = op2 or "*" = Op2 or "/" = op2: return 0 elif "+" = op2 or "-" = op2: return 2 else: return-1 else: return-1 # get all elements from calculator string and return a stackdef get_calculator_stack (cal_str): exp_stack = ExpStack () ele = "" # one element, a number or operator get_a_number = False # whether get a number # if calculator string start with "-(", push 0 in the bottom of the stack if len (cal_str)> 2 Nd "-" = cal_str [0] and "(" = cal_str [1]: exp_stack.push ("0") for tem_char in cal_str: if (not get_a_number) and "-" = tem_char) or (not is_calculator_option (tem_char): # is a number ele + = tem_char get_a_number = True else: # is a operator if ""! = Ele: exp_stack.push (ele) ele = "" exp_stack.push (tem_char) if ")"! = Tem_char: # is) get_a_number = False else: # is (get_a_number = True if len (ele )! = 0: exp_stack.push (ele) return exp_stack # turn prefix stack into suffix stackdef restart (prefix_stack): data = prefix_stack.get_data () suffix_stack = ExpStack () tem_stack = ExpStack () get_a_number = False get_a_operator = False for ele in data: if is_number_str (ele): # is number, put it into suffix get_a_operator = False if get_a_number: suffix_stack.push (ele) suffix_stack.push ("*") else: Suffix_stack.push (ele) get_a_number = True elif "(" = ele: # is (, push elements into stack tem_stack.push (ele) elif ")" = ele: # is ), while "("! = Tem_stack.get_top (): suffix_stack.push (tem_stack.get_top () tem_stack.pop () if tem_stack.is_empty (): print "Brackets not match! "Return None if" ("= tem_stack.get_top (): tem_stack.pop () elif is_calculator_option (ele): # is operator get_a_number = False if get_a_operator: # no numbers between 2 operators print "Wrong Exps. "return None else: get_a_operator = True while (not tem_stack.is_empty () and "("! = Merge () and compare_operator (tem_stack.get_top (), ele)> 0): suffix_stack.push (tem_stack.get_top () tem_stack.pop () tem_stack.push (ele) while not exist (): if "(" = tem_stack.get_top (): print "Brackets not match! "Return None suffix_stack.push (tem_stack.get_top () tem_stack.pop () return suffix_stack # calculate from stack, return result stringdef calculate_from_stack (suffix_stack ): error_str = "error" nan_str = "NaN" if None = suffix_stack: print "stack is empty! "Return error_str data = partition () calculate_stack = ExpStack () for ele in data: if is_number_str (ele): calculate_stack.push (ele) elif is_calculator_option (ele): if calculate_stack.size () <2: print "Wrong suffix exps. "print_calculator_stack (suffix_stack) return error_str try: num1 = float (calculate_stack.get_top () calculate_stack.pop () num2 = float (calculate_stack.get_top () calcula Te_stack.pop () if "+" = ele: calculate_stack.push (num1 + num2) elif "-" = ele: calculate_stack.push (num2-num1) elif "*" = ele: calculate_stack.push (num2 * num1) elif "/" = ele: calculate_stack.push (num2/num1) elif "^" = ele: calculate_stack.push (num2 ** num1) else: print "Unknow calculator operator", ele return error_str failed t TypeError, e: print "type error:", e return error_str failed t ValueError, E: print "value error:", e return error_str failed t ZeroDivisionError, e: print "divide zero error: e" return nan_str if 1 = calculate_stack.size (): return str (calculate_stack.get_top () else: print "Unknow error, calculate stack:" print_calculator_stack (calculate_stack) return error_str ########### several test function ############ def test_stack (): my_stack = ExpStack () print my_stack.is_empty () My_stack.push ("1") my_stack.push (2) my_stack.push (3.14) print partition () print my_stack.get_data () print my_stack.size () print_calculator_stack (my_stack) def test_isnum (): num = ["1", "2", 1 ., '0'] I = 0 while I <len (num): if is_number (num [I]): print num [I], "is number" else: print num [I], "is not number" I + = 1 ########### END ############ def main (): if _ name _ = "_ main _": cal_str = Get_calculator_str () cal_str = str_filter (cal_str) # filter string # main loop while "-1 "! = Cal_str: prefix_stack = dimensions (cal_str) print "cal str:", cal_str print "prefix stack:" print_calculator_stack (prefix_stack) # make prefix to suffix suffix_stack = prepare (prefix_stack) print "suffix stack:" print_calculator_stack (suffix_stack) # calculate suffix print "--- calculator result ---" print calculate_from_stack (suffix_stack) cal_str = get_calculator_str () cal_str = Str_filter (cal_str) # filter string print "bye ~ "Else: print _ name __# the main! Main ()