Implementing User Input to Choose the File Name

If you want to write program that gives option to a user to type the name of the specific file than you have to implement know built in function raw_input(). It would be more useful to ask the user to enter specific file and then perform some operation on that file. This is very simple procedure and is given below:

filename = raw_input('Enter the file name: ')
fname = open(filename)
count = 0
for line in fname:
    if line.startswith('Python '):
        count = count + 1
print 'There where' , count , 'subject lines in', fname

Result of previous code when executed is given below.

Enter the file name: P-files.txt

There where 3 subject lines in