A simple python calculator using lambda expressions

calc.py

operations = {
    "+": lambda x, y: x + y,
    "-": lambda x, y: x - y,
    "/": lambda x, y: x / y,
    "*": lambda x, y: x * y
}

def calculate(expr):
    numxChars = ""
    operation = None
    numyChars = ""
    for char in expr:
        if char.isdigit():
            if operation is None:
                numxChars += char
            else:
                numyChars += char
        elif char in operations:
            operation = char
        elif char.isspace:
            pass
        else:
            raise Exception("invalid charecter: " + char)
    return operations[operation](int(numxChars), int(numyChars))
    
print calculate(raw_input("Input? "))
            

example

$ python calc.py
Input? 1 + 1
2
Input? 2/1
2
Input? 3-4
-1
Input? 7*5
35

Can i using this case for big number have 1000 charactor?

@akash-mahanty it does not support parenthesis. Quite poor implementation.