Python POS转SOP用法及代码示例

# Python code to convert standard POS form 
# to standard SOP form 
  
# Function to calculate no. of variables 
# used in POS expression 
def count_no_alphabets(POS): 
    i = 0
    no_var = 0
  
    # As expression is standard so total no. 
    # of alphabets will be equal 
    # to alphabets before first '.' character 
    while (POS[i]!='.'): 
  
        # checking if character is alphabet         
        if (POS[i].isalpha()):     
            no_var+= 1
        i+= 1
    return no_var 
  
# Function to calculate the max terms in integers 
def Cal_Max_terms(Max_terms, POS): 
    a = "" 
    i = 0
    while (i<len(POS)): 
        if (POS[i]=='.'): 
  
            # converting binary to decimal                 
            b = int(a, 2) 
  
            # insertion of each min term(integer) into the list                 
            Max_terms.append(b) 
  
            # empty the string         
            a =""                         
            i+= 1
              
        elif(POS[i].isalpha()): 
  
            # checking whether variable is complemented or not 
            if(i + 1 != len(POS) and POS[i + 1]=="'"): 
  
                # concatenating the string with '0' 
                a += '1' 
  
                # incrementing by 2 because 1 for alphabet and 
                # another for "'"                        
                i += 2                            
            else: 
  
                # concatenating the string with '1' 
                a += '0'                        
                i += 1
        else: 
            i+= 1
  
    # insertion of last min term(integer) into the list     
    Max_terms.append(int(a, 2))         
  
# Function to calculate the min terms in binary then 
# calculate SOP form of POS 
def Cal_Min_terms(Max_terms, no_var, start_alphabet): 
  
    # declaration of the list 
    Min_terms =[] 
  
    # calculation of total no. of terms that can be 
    # formed by no_var variables                 
    max = 2**no_var                 
    for i in range(0, max): 
  
        # checking whether the term is not 
        # present in the max terms 
        if (Max_terms.count(i)== 0): 
  
            # converting integer to binary and then 
            # taking the value from 2nd index as 1st 
            # two index contains '0b' 
            b = bin(i)[2:] 
  
            # loop used for inserting 0's before the 
            # binary value so that its length will be 
            # equal to no. of variables present in 
            # each product term         
            while(len(b)!= no_var): 
                b ='0'+b 
  
            # appending the max terms(integer) in the list 
            Min_terms.append(b)     
  
    SOP = "" 
  
    # loop till there are min terms                         
    for i in Min_terms: 
  
        # acquire the starting variable came from 
        # main function in every product term             
        value = start_alphabet 
  
        # loop till there are 0's or 1's in each min term     
        for j in i: 
  
            # checking for complement variable to be used                 
            if (j =='0'): 
  
                # concatenating value, ' and + in string POS                 
                SOP = SOP + value+"'"
  
            # checking for uncomplement variable to be used     
            else: 
  
                # concatenating value and + in string POS                     
                SOP = SOP + value 
  
            # increment the alphabet by 1     
            value = chr(ord(value)+1) 
  
        # appending the SOP string by '+" after 
        # every product term                 
        SOP = SOP+ "+"
  
    # for discarding the extra '+' in the last                 
    SOP = SOP[:-1]                         
    return SOP 
  
# main function 
def main(): 
      
    # input1 
    POS_expr ="(A+B+C).(A+B+C').(A+B'+C).(A'+B + C)"
    Max_terms = [] 
      
    no_var = count_no_alphabets(POS_expr) 
    Cal_Max_terms(Max_terms, POS_expr) 
    SOP_expr = Cal_Min_terms(Max_terms, no_var, POS_expr[1]) 
      
    print("Standard SOP form of " + POS_expr + " ==> " + SOP_expr) 
  
    # input2 
    POS_expr ="(A + B).(A'+B')"
    Max_terms = [] 
      
    no_var = count_no_alphabets(POS_expr) 
    Cal_Max_terms(Max_terms, POS_expr) 
    SOP_expr = Cal_Min_terms(Max_terms, no_var, POS_expr[1]) 
      
    print ("Standard SOP form of " + POS_expr + " ==> " + SOP_expr) 
  
# Driver code 
if __name__=="__main__": 
    main()