"fundamentals of compiling"'s homework, count the variable

lib_1.py

#!/usr/bin/env python2.7
# -*- coding:utf-8 -*-

# __author__ = "Shaun"

import sys


VAR = []


def read_source(filename):
    """
    read source from file
    input: file name
    output: a long string of file
    """
    source = None
    try:
        f = open(filename, 'r+')
        source = f.read()
        f.close()
    except IOError:
        print "please input correct file name or path!"
    finally:
        return source


def deal_file(code):
    """
    deal with the file
    input: a string of file
    output: a dict about the variable count
    """
    line_list = code.split("\n")
    for line in line_list:
        if line != "":
            get_var(line)
    deal_symbol()
    count_dict = count_var(line_list)
    return count_dict


def get_var(line):
    """
    Find the variable which was defined in the source
    input: a line of the file
    no output
    """
    word_list = line.split(" ")
    if word_list[0].strip(" ") == "Var" or word_list[0].strip(" ") == "Const":
        for word in word_list[1:]:
            if word.find(',') != '-1':
                var_list = word.split(',')
                VAR.extend(var_list)


def deal_symbol():
    """
    delete some symbol in the variable
    no input
    no output
    """
    for i, var in enumerate(VAR):
        if var.endswith(";"):
            VAR[i] = VAR[i][:-1]
        index = var.find("=")
        if index != -1:
            VAR[i] = VAR[i][0:index]


def count_var(line_list):
    """
    count the variable according to some rules
    input: a list of the file's line
    output: a dict which stored variable's count
    """
    count_list = []
    count_dict = {}
    for line in line_list:
        for var in VAR:
            lower = var.lower()
            upper = var.upper()
            if line.find(lower) != -1:
                is_alnum_1 = line[line.find(lower)-1].isalpha() and line[line.find(lower)-1].isdigit()
                is_alnum_2 = line[line.find(lower)+1].isalpha() and line[line.find(lower)+1].isdigit()
                if not is_alnum_1 and not is_alnum_2:
                    count_list.append(var)
            elif line.find(upper) != -1:
                is_alnum_1 = line[line.find(upper)-1].isalpha() and line[line.find(upper)-1].isdigit()
                is_alnum_2 = line[line.find(upper)+1].isalpha() and line[line.find(upper)+1].isdigit()
                if not is_alnum_1 and not is_alnum_2:
                    count_list.append(var)
    for i in VAR:
        count = count_list.count(i)
        count_dict[i] = count

    return count_dict


def main():
    arg = sys.argv
    if len(arg) == 2:
        file_name = arg[1]
        code = read_source(file_name)
    else:
        print "arguments error!"
        return 0

    count = deal_file(code)

    print count


if __name__ == "__main__":
    main()