Python calculator (Day 4), python Calculator

Python calculator (Day 4), python Calculator

Job:

Use regular expressions and recursion to implement the calculator function.

 

Implementation:

1. Implement calculation with parentheses

2. Implement functions such as exponential, addition, subtraction, multiplication, division, and remainder

I. instance description:

This instance has written a version by itself, but there is still a bug, for example,-2-2 and other computing problems. Therefore, in addition to the code of Wu SIR, the function such as index and remainder is added.

Idea Of This calculator:
1. Recursively search for expressions that only contain numbers and operators and calculate the results
2. Since decimal places are ignored in integer calculation, all numbers are considered floating-point operations to retain decimal places.
Technology used:
1. Regular Expression
2. Recursion

 

Ii. flowchart:

#! /Usr/bin/python27 # _ * _ coding = UTF-8 _ * _ '''created on August 1 @ author: Wang kai''' ''' This calculator concept: 1. recursive search expression contains only numbers and operators. Calculation Result 2. Since integer calculation ignores decimal places, all numbers are considered floating-point operations, to retain decimal use technology: 1. Regular Expression 2. Recursive Execution process is as follows: * ****************** calculate the expression: 1-2*(60-30 + (-40.0/5) * (9-2*5/3 + 7/3*99/4*2998 + 10*568/14)-(-4*3)/(16-3*2 )) * ****************** before: ['1-2*(60-30 + (-40.0/5) * (9-2*5/3 + 7/3*99/4*2998 + 10*568/14)-(-4*3)/(16-3 * 2) ']-40.0/5 =-8.0 after: ['1-2*(60-30 +-8.0*(9-2*5/3 + 7/3*99/4*2998 + 10*568/14)-(-4*3) /(16-3*2) '] =========== last computing end ========== before: ['1-2*(60-30 +-8.0*(9-2*5/3 + 7/3*99/4*2998 + 10*568/14)-(-4*3) /(16-3*2) '] 9-2*5/3 + 7/3*99/4*2998 + 10*568/14 = 173545.880953 after: ['1-2*(60-30 +-8.0*173545.880953)-(-4*3)/(16-3*2 )) '] ========== last computing end ========== before: ['1-2*(60-30 +-8.0*173545.880953)-(-4*3)/(16-3*2) '] 60 -30 +-8.0*173545.880953 =-1388337.04762 after: ['1-2*(-1388337.04762-(-4*3)/(16-3*2 )) '] ========== last computing end ========== before: ['1-2 * (-1388337.04762-(-4*3)/(16-3*2) ']-4*3 =-12.0 after: ['1-2*(-1388337.04762 -- 12.0/(16-3*2 )) '] ========== last computing end ========== before: ['1-2*(-1388337.04762 -- 12.0/(16-3*2) '] 16-3*2 = 10.0 after: ['1-2*(-1388337.04762 -- 12.0/10.0) '] =========== last computing end ========== before: ['1-2*(-1388337.0 4762--12.0/10.0) ']-1388337.04762 -- 12.0/10.0 =-1388335.84762 after: ['1-2 *-1388335.84762 '] =========== last computing end ========= my computing results: 2776672.69524 ''' import re, OS, sysdef compute_exponent (arg): "operation index: param expression: return: calculation Result "" val = arg [0] pattern = re. compile (R' \ d + \.? \ D * [\ *] {2} [\ + \-]? \ D + \.? \ D * ') mch = pattern. search (val) if not mch: return content = pattern. search (val ). group () if len (content. split ('**')> 1: n1, n2 = content. split ('**') value = float (n1) ** float (n2) else: pass before, after = pattern. split (val, 1) new_str = "% s" % (before, value, after) arg [0] = new_str compute_exponent (arg) def compute_mul_div (arg ): "Operation multiplication and division: param expression: return: calculation result" val = arg [0] patte Rn = re. compile (R' \ d + \.? \ D * [\ * \/\ % \/] + [\ + \-]? \ D + \. * \ d * ') mch = pattern. search (val) if not mch: return content = pattern. search (val ). group () if len (content. split ('*')> 1: n1, n2 = content. split ('*') value = float (n1) * float (n2) elif len (content. split ('//')> 1: n1, n2 = content. split ('/') value = float (n1) // float (n2) elif len (content. split ('%')> 1: n1, n2 = content. split ('%') value = float (n1) % float (n2) elif len (content. split ('/')> 1: n1, N2 = content. split ('/') value = float (n1)/float (n2) else: pass before, after = pattern. split (val, 1) new_str = "% s" % (before, value, after) arg [0] = new_str compute_mul_div (arg) def compute_add_sub (arg ): "Operation addition and subtraction: param expression: return: calculation result" while True: if arg [0]. _ contains _ ('+-') or arg [0]. _ contains _ ("++") or arg [0]. _ contains _ ('-+') or arg [0]. _ contains _ ("--"): arg [0] = arg [0 ]. Replace ('+-', '-') arg [0] = arg [0]. replace ('++', '+') arg [0] = arg [0]. replace ('-+', '-') arg [0] = arg [0]. replace ('--', '+') else: break if arg [0]. startswith ('-'): arg [1] + = 1 arg [0] = arg [0]. replace ('-', '&') arg [0] = arg [0]. replace ('+', '-') arg [0] = arg [0]. replace ('&', '+') arg [0] = arg [0] [1:] val = arg [0] pattern = re. compile (R' \ d + \.? \ D * [\ + \-] {1} \ d + \.? \ D * ') mch = pattern. search (val) if not mch: return content = pattern. search (val ). group () if len (content. split ('+')> 1: n1, n2 = content. split ('+') value = float (n1) + float (n2) else: n1, n2 = content. split ('-') value = float (n1)-float (n2) before, after = pattern. split (val, 1) new_str = "% s" % (before, value, after) arg [0] = new_str compute_add_sub (arg) def compute (expression ): "Operation addition, subtraction, multiplication, division: param Expression: return: compute_exponent # compute_mul_div (indium) in the processing expression) # add and subtract compute_add_sub (indium) if divmod (indium [1], 2) [1] = 1: result = float (indium [0]) of the processing expression result = result *-1 else: result = float (indium [0]) return resultdef exec_bracket (expression): "" recursive processing of parentheses and calculation: param expression: return: The final calculation result is "" pattern = re. compile (R' \ ([\ + \-\ * \/\ % \/\/\* \ *] * \ D + \. * \ d *) {2,} \) ') # If no parentheses exist in the expression, directly call the function responsible for calculation and return the expression result, for example: 2*1-82 + 444 # if not re. search ('\ ([\ + \-\ * \/] * \ d + \. * \ d *) {2,} \) ', expression): if not pattern. search (expression): final = compute (expression) return final # obtain the first parentheses containing only numbers/decimals and operators # For example: #['1-2*(60-30 + (-40.0/5) * (9-2*5/3 + 7/3*99/4*2998 + 10*568/14 )) -(-4*3)/(16-3*2) '] # Find Out: (-40.0/5) content = pattern. search (expression ). group () # split expression, I .e :# Set ['1-2*(60-30 + (-40.0/5) * (9-2*5/3 + 7/3*99/4*2998 + 10*568/14 )) -(-4*3)/(16-3*2) '] # Separate the three parts: ['1-2*(60-30 + (-40.0/5) * (9-2*5/3 + 7/3*99/4*2998 + 10*568/14 )) -(-4*3)/(16-3*2) '] before, nothing, after = pattern. split (expression, 1) print ('before: ', expression) content = content [1: len (content)-1] # calculation, extracted representation (-40.0/5), and the live result is:-40.0/5 =-8.0 ret = compute (content) print ('% s = % s' % (content, ret) # splice the execution result, ['1-2*(60-30 + (-8.0*(9-2*5/3 + 7/3*99/4*2998 + 10*568/14)-(-4*3) /(16-3*2) '] expression = "% s" % (before, ret, after) print ('after:', expression) print ("=" * 10, 'previous result is ', "=" * 10) # The loop continues the next brace processing operation. This contains the processed expression, that is: #['1-2*(60-30 +-8.0*(9-2*5/3 + 7/3*99/4*2998 + 10*568/14 )) -(-4*3)/(16-3*2) '] # This repeats until the expression no longer contains the brackets return exec_bracket (expression) # purpose of using _ name _: # Only python index is executed. the following code only Run # if others import this module, the following code does not run if _ name _ = "_ main _": flag = True OS. system ('clear ') ### clear screen ### print ('\ n ============================ ========================================= ') print ('\ 033 [33 m welcome calculator: \ 033 [0m ') print ('\ n ======================================== ============================= ') while flag: calculate_input = raw_input ('\ 033 [32 m, enter the calculated expression | (Exit: q) \ 033 [0m') calculate_input = re. sub ('\ s *', '', calculate_indium Ut) if len (calculate_input) = 0: continue elif calculate_input = 'q': sys. exit ('exit Project') elif re. search ('[^ 0-9 \. \-\ + \ * \/\ % \/\ * \ (\)] ', calculate_input): print (' \ 033 [31 m input error, please enter it again !!! \ 033 [0m') else: result = exec_bracket (calculate_input) print ('the expression result is % s' % result)Calculator

 

4. There is no big difference between python2.7 and python3.4, so you only need one version.