count registers in C code -- registers has one pattern

#!/bin/python
import os
import re


words_dict={}

def grep_reg(key,path):
        cmd="grep "+key+" -r "+path+" > alex.txt"
        print cmd
        os.system(cmd)

def match_reg(f,key):
        reg_key = key+r"\.\w+"
        reg_pattern = re.compile(reg_key)
        for eachline in f:
                print eachline
                reg_list = reg_pattern.findall(eachline)
                if reg_list:
                        print reg_list
                        reg_name = "".join(reg_list)
                        print reg_name
                        if reg_name in words_dict.keys():
                                words_dict[reg_name] +=1
                        else:
                                words_dict[reg_name] = 1

def print_reg():
        for word,count in words_dict.items():
                print('%-20s:' % word,count)

if __name__ == "__main__":
        key=raw_input('please input reg key:')
        path=raw_input('please input path:')
        grep_reg(key,path)
        f=open("alex.txt")
        match_reg(f,key)
        print_reg()