Parser.py

#!/usr/bin/env python
def findNextNumber():
    floatnum = 0
    return floatnum
def parsing(string):
    container = []
    stacking = []
    numparse = ""
    for item in string:
        if item.isalnum() or item == "." :
            numparse += item
        else:
            if numparse != "":
                container.append(numparse)
            numparse = ""
            stackOperation(item, stacking, container)
    if numparse:
        container.append(numparse)
    stackOperation("~", stacking, container)
    return container
def stackOperation(item , stacking, container):
    if stacking == [] :
        stacking.append(item)
    else:
        if item == ")":
            while 1:
                if stacking[-1] == "(" :
                    stacking.pop()
                    break
                elif not stacking:
                    break
                else:
                    container.append(stacking.pop())
        elif item == "~":
            while 1:
                if not stacking:
                    break
                elif stacking[-1] == "(" :
                    stacking.pop()
                else:
                    container.append(stacking.pop())
        elif priority(stacking[-1] ) == 4:
            stacking.append(item);
        elif priority(item) > priority(stacking[-1])  :
            stacking.append(item)
        elif priority(item) < priority(stacking[-1])  :
            while 1:
                if not stacking:
                    break
                elif stacking[-1] == "(" :
                    break
                else:
                    container.append(stacking.pop())
            stacking.append(item)
    return
def calculate(postfix):
 
    while 1:
        area2BModified = []        
        i = 0
        for item in postfix:
            #print postfix[i][0].isalnum()
            if not item[0].isalnum():
                if postfix[i-1][0].isalnum() and postfix[i-2][0].isalnum():    
                    area2BModified.append(i)
            i = i + 1
        #for item in area2BModified:
        #    print item
        #print len(postfix)
        #for item in postfix:
        #    print item
        #print "\n"
        if len(postfix) == 1:
            break
        count = 0
        for item in area2BModified:
            #print item
            item = item - count
            #print float(postfix[item - 1])
            #print postfix[item]
            #print float(postfix[item - 2])
            temp = operationPart(postfix[item - 2], postfix[item - 1], postfix[item])
            postfix.pop(item )
            postfix.pop(item - 1)
            postfix.pop(item - 2)
            postfix.insert(item - 2, repr(temp))
            count = count + 2
 
        del area2BModified[:]
 
    return postfix
 
def operationPart(num1, num2, operand):
    if operand == "-" :
        return float(num1) - float(num2)
    elif operand == "+" :
        return float(num1) + float(num2)
    elif operand == "*" :
        return float(num1) * float(num2)
    elif operand == "/" :
        return float(num1) / float(num2)
    return
 
def priority(item):
    if item == "-" :
        return 1
    elif item == "+" :
        return 2
    elif item == "*" :
        return 3
    elif item == "/" :
        return 4
    elif item == "(" :
        return 5
    return
 
 
 
a = "2.5+3*(59-23)+4/2"
postfix = parsing(a)
#for item in postfix:
#    print item
#print float(postfix[2])
result = calculate(postfix)
print result[0]
#print a[1].isalnum()
#lalalulu = [3,4,5,6]
#print lalalulu[-1]