How to count lines in a text file ?

[Ling Lee]

Hi all.

I'm trying to write a program that:
1) Ask me what file I want to count number of lines in, and then counts the 
lines and writes the answear out.

2) I made the first part like this:

in_file = raw_input("What is the name of the file you want to open: ")
in_file = open("test.txt","r")
text = in_file.read()

3) I think that I have to use a for loop ( something like: for line in text: 
count +=1)
Or maybee I have to do create a def: something like: ( def loop(line, 
count)), but not sure how to do this properly.
And then perhaps use the readlines() function, but again not quite sure how 
to do this. So do one of you have a good idea.

Thanks for all help