Converts string to integer

str_to_int.py

"""
Convert string to integer
"""
import unittest

class TestStringMethods(unittest.TestCase):

    def test1(self):
        self.assertEqual(myInt("123"), 123)

    def test2(self):
        self.assertEqual(myInt("-1"), -1)

    def test3(self):
        self.assertEqual(myInt("0"), 0)

    def test4(self):
        self.assertEqual(myInt("-0"), 0)

    def test5(self):
        self.assertRaises(TypeError, myInt, "")

    def test6(self):
        self.assertRaises(TypeError, myInt, "12q3")



def myInt(s):
    num = 0
    l = len(s)
    if l == 0:
        raise TypeError("String must be non-empty")

    sign = 1

    if s[0] == "-":
        sign = -1
        s = s[1:]

    for i in s:
        if ord(i) in range(ord("0"), ord("9") + 1):
            digit = ord(i) - ord("0")
            num = num*10 + digit

        else:
            raise TypeError("String must contain only digits and minus sign")

    return sign * num

unittest.main()

print myInt("-112490") # -112490