Lexer

lex.py

string = '''
interface NamedEntity {
    name: String
}
'''

state = 0
index = 0
for position in range(len(string)):
    character = string[position]
    if state == 0:
        if 'A' <= character <= 'Z' or 'a' <= character <= 'z':
            state = 1
            index = position
        elif character == ' ' or character == '\n':
            pass
        else:
            state = 2
            index = position
    elif state == 1:
        if 'A' <= character <= 'Z' or 'a' <= character <= 'z':
            pass
        elif character == ' ' or character == '\n':
            print string[index:position]
            state = 0
        else:
            print string[index:position]
            state = 2
            index = position
    else:
        if 'A' <= character <= 'Z' or 'a' <= character <= 'z':
            print string[index:position]
            state = 1
            index = position
        elif character == ' ' or character == '\n':
            print string[index:position]
            state = 0
        else:
            print string[index:position]
            state = 2
            index = position