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```# Infix Expression Evaluation
# The expression must contain only positive numbers,
# aritmetic operators and parentheses.
# FB - 20151107
def isOp(c):
if c != "": return (c in "+-*/")
else: return False

def pri(c): # operator priority
if c in "+-": return 0
if c in "*/": return 1

def isNum(c):
if c != "": return (c in "0123456789.")
else: return False

def calc(op, num1, num2):
if op == "+": return str(float(num1) + float(num2))
if op == "-": return str(float(num1) - float(num2))
if op == "*": return str(float(num1) * float(num2))
if op == "/": return str(float(num1) / float(num2))

def Infix(expr):
expr = list(expr)
stackChr = list() # character stack
stackNum = list() # number stack
num = ""
while len(expr) > 0:
c = expr.pop(0)
if len(expr) > 0: d = expr[0]
else: d = ""
if isNum(c):
num += c
if not isNum(d):
stackNum.append(num)
num = ""
elif isOp(c):
while True:
if len(stackChr) > 0: top = stackChr[-1]
else: top = ""
if isOp(top):
if not pri(c) > pri(top):
num2 = stackNum.pop()
op = stackChr.pop()
num1 = stackNum.pop()
stackNum.append(calc(op, num1, num2))
else:
stackChr.append(c)
break
else:
stackChr.append(c)
break
elif c == "(":
stackChr.append(c)
elif c == ")":
while len(stackChr) > 0:
c = stackChr.pop()
if c == "(":
break
elif isOp(c):
num2 = stackNum.pop()
num1 = stackNum.pop()
stackNum.append(calc(c, num1, num2))

while len(stackChr) > 0:
c = stackChr.pop()
if c == "(":
break
elif isOp(c):
num2 = stackNum.pop()
num1 = stackNum.pop()
stackNum.append(calc(c, num1, num2))

return stackNum.pop()

# TEST
expr = "1.7+2.8*3.6/(0-9.4)+5/(0.36-7.7)/9.12*11"
print "EXPR: " + expr
print "EVAL: " + str(eval(expr))
print "INFX: " + Infix(expr)
```