How Do I get this while loop to execute the function multiple times?

#The dictionary:
f = open("glossary.txt", "r")

num_lines = sum(1 for line in open("glossary.txt"))

def readLines():
    global my_glossary
    global line
    global words
    global f
    f = open("glossary.txt", "r")
    line = f.readline()
    words = line.split(",")
    my_glossary = {}
    my_glossary[words[0]]=words[1]
    line = f.readline()
    words = line.split(",")
    my_glossary[words[0]]=words[1]

while num_lines > 0:
    readLines()
    num_lines -=1